@article{liu_liu_feng_koch_jing_2023, title={Mechanical properties and microstructure of the heterogeneous DZ2 axle steel under high-strain-rate compression at ambient temperature}, volume={26}, ISSN={["2214-0697"]}, DOI={10.1016/j.jmrt.2023.09.192}, abstractNote={This study aims to clarify the mechanical properties and deformation characteristics of the newly-developed DZ27CrNiMo (DZ2) axle steel for the China standard electric multiple units under dynamic loadings along the diameter direction of the axle at room temperature. The DZ2 axle steel has a heterogeneous band structure consisting of equiaxed grain and lath morphology tempered martensite. When being impacted at the strain rate range from 500 s-1 to 2440 s-1, its yield strength, compressive strength, and plastic strain increase. The flow stress upturn after yielding mainly depended on the strain rate effect rather than the work hardening due to the suppressed dislocation cross-slip. Meanwhile, the steady plasticity was consistent with the presence of uniformly distributed dislocations and microbands within the heterogeneous laminates. Although the nanoscale adiabatic shear bands (ASBs) and micro-cracks were found to initiate at the high strain rate of 2440 s-1, their propagation could be inhibited by the hard-tempered sorbate laths. As a consequence, an excellent resistance for impact-induced fracture was realized in DZ2 axle steel. Taking the thermal activation damage evolution into account, a modified Zerilli-Armstrong (ZA) constitutive model was proposed to describe the dynamic mechanical behavior of DZ2 axle steel. The modeling results were consistent with the experimental data, indicating a high prediction accuracy and good application availability in the operation and maintenance of DZ2 axle.}, journal={JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T}, author={Liu, Ying and Liu, Xiaobo and Feng, Chao and Koch, Carl C. and Jing, Lin}, year={2023}, pages={8456–8471} }
 @article{escobar_silverstein_ishrak_li_soulami_li_yu_mathaudhu_ortiz_koch_et al._2023, title={Microstructural evolution in shear-punch tests: A comparative study of pure Cu and Cu-Cr alloy}, volume={886}, ISSN={["1873-4936"]}, url={https://doi.org/10.1016/j.msea.2023.145715}, DOI={10.1016/j.msea.2023.145715}, abstractNote={Understanding the mechanisms behind microstructural evolution during shear deformation has been a long-standing area of interest. However, establishing a connection between microstructure, mechanical properties, and the extent of shear deformation is challenging and requires refined experimental approaches. Shear-punch testing (SPT) provides a controlled method to introduce shear into small volumes of material that later can be subjected to detailed microstructural characterization. In this study, we utilize an SPT device to induce shear deformation to pure copper (Cu) and a binary copper-chromium (Cu-Cr) alloy. Electron backscatter diffraction and transmission electron microscopy were used to study the mechanisms of plastic deformation after SPT. Our results indicate that shear deformation of pure Cu produces a dense network of intercepting microshear bands upon sustained deformation. Twin boundaries in annealed Cu undergo transformation into high-angle grain boundaries due to simultaneous deviation from the axis-angle pair condition of 60° misorientation on [111] direction. The presence of 50 vol% Cr particles in the soft Cu matrix altered the shear deformation mechanism. Preferential deformation of the Cu matrix in Cu-Cr alloy led to accelerated shear-induced formation of low and high-angle grain boundaries and subsequent grain refinement. Comparatively, insignificant grain refinement occurred in pure Cu samples even at a strain ∼10 times larger (ε = 4.73) than that of the Cu-Cr case (ε = 0.42). This study sheds light on the microstructural evolution of Cu during shear deformation and highlights the significant influence of a hard second phase in modifying the microstructural response mechanisms of a softer matrix.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Escobar, Julian and Silverstein, Joshua and Ishrak, Farhan and Li, Lei and Soulami, Ayoub and Li, Shuang and Yu, Anqi and Mathaudhu, Suveen and Ortiz, Angel and Koch, Carl and et al.}, year={2023}, month={Oct} }
 @article{cai_li_liu_si_gu_zhou_cheng_koch_2022, title={Cryogenic reciprocating torsion induced nanoscale precipitation in aluminum wire with exceptional strength and electrical conductivity}, volume={860}, ISSN={["1873-4936"]}, url={https://doi.org/10.1016/j.msea.2022.144276}, DOI={10.1016/j.msea.2022.144276}, abstractNote={Cryogenic reciprocating torsion (CRT) was used to trade off strength and electrical conductivity in aluminum wires. Compared with the initial sample, the CRT processed aluminum wires possess higher strength without significant sacrifice of electrical conductivity. The ultimate tensile strength increases by 76% with a slight decrement of 1% IACS in electrical conductivity. Microstructural characterizations show that CRT induces multiple gradient structures (MGSs) on the cross-section of aluminum wires: dislocation density gradient, grain size gradient, and precipitate size gradient. In particular, a bimodal distribution of precipitate size was observed in CRT processed aluminum wires. A theoretical model considering the above microstructures was proposed to explain the excellent properties. The experimental results validate the reasonability of the present model. The further theoretical analyses reveal that nanoscale precipitates contribute more to the exceptional strength and electrical conductivity than other microstructures.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Cai, S. L. and Li, D. Q. and Liu, S. C. and Si, J. J. and Gu, J. and Zhou, L. X. and Cheng, Y. F. and Koch, C. C.}, year={2022}, month={Dec} }
 @article{cai_li_liu_cheng_li_koch_2022, title={Multiple gradient structures driving higher tensile strength and good capacity to absorb e d energy in aluminum wire processed by cryogenic pre-torsion}, volume={210}, ISSN={["1872-8456"]}, url={http://dx.doi.org/10.1016/j.scriptamat.2021.114436}, DOI={10.1016/j.scriptamat.2021.114436}, abstractNote={Aluminum wire with multiple gradient structures (MGSs) was processed by cryogenic pre-torsion. Microstructural characterizations illustrate that grain size gradient, dislocation density gradient, precipitate size gradient, and precipitate volume fraction gradient were produced during the cryogenic pre-torsion process of aluminum wire. Uniaxial tensile tests reveal that the multiple gradient structured aluminum wire possesses higher strength without compromising the capacity to absorbed energy. A theoretical model considering these MGSs was proposed to explain the excellent mechanical properties. The theoretical analyses reveal that the high strength is attributed to the fine grains, high dislocation density, and large volume fraction of precipitate. The gradient yield stress resulting from MGSs promotes the accumulation of geometrically necessary dislocations (GNDs). This provides extra strain hardening capability for improving the capacity to absorbed energy.}, journal={SCRIPTA MATERIALIA}, publisher={Elsevier BV}, author={Cai, S. L. and Li, D. Q. and Liu, S. C. and Cheng, Y. F. and Li, J. H. and Koch, C. C.}, year={2022}, month={Mar} }
 @article{cai_wan_hao_koch_2020, title={Dual gradient microstructure to simultaneously improve strength and electrical conductivity of aluminum wire}, volume={783}, ISSN={["1873-4936"]}, url={http://dx.doi.org/10.1016/j.msea.2020.139308}, DOI={10.1016/j.msea.2020.139308}, abstractNote={High strength and high electrical conductivity are needed for the usage of aluminum wire in high-voltage lines. Strength and electrical conductivity are contradictory in metallic materials. Improving strength comes with the sacrifice of electrical conductivity. Here we produced a dual gradient microstructure to improve the strength of aluminum wire without compromising electrical conductivity. Aluminum wires with gradient microstructures and dual gradient microstructures were processed through clockwise torsion and subsequent anti-clockwise torsion. Compared with the gradient microstructural aluminum, aluminum with dual gradient microstructures possesses higher strength and higher electrical conductivity. Microstructural characterizations and numerical simulations further reveals that dual gradient grain size provides extra strain hardening and less electrical resistivity. This explains the high strength and high electrical conductivity in aluminum wire with dual gradient microstructure.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Cai, S. L. and Wan, J. C. and Hao, Y. J. and Koch, C. C.}, year={2020}, month={May} }
 @article{liu_zheng_wu_koch_han_zhang_liu_zhang_2020, title={Grain refinement induced friction reduction and anti-wear performances of electrodeposited graphene/Ni composites with low content reduced graphene oxide}, volume={826}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2020.154080}, abstractNote={Graphene and its derivatives have attained a considerable amount of popularity as effective reinforcements in the electrodeposited nickel (Ni) matrix composites for lubrication. However, the composites suffer from certain challenges, such as the agglomeration of graphene nanosheets in the electrodeposition process and the uncertain role of graphene on the friction reduction and wear resistance during sliding. By using a polyvinylpyrrolidone assisted reduction method to improve the dispersity of reduced graphene oxide (RGO) in the electrolyte, we prepare the bulk RGO/Ni composites with different RGO adding amount and perform a complete research on the tribological behaviours. Our work reveals that although an extremely low amount of RGO nanosheets (carbon content below 0.018%) have been incorporated into the Ni matrix, it induces significant grain refinement and friction reduction effects. Compared with the RGO-free Ni deposit, the friction coefficient and wear rate of the composite is reduced by 25.6% and 27.5%, respectively. The improved tribological properties are ascribed to the fine-grain strengthening effect and the formation of a continuous easy-shear nickel oxide film on the contact surface. This finding offers a new view on the wear mechanism of graphene/Ni composites with low graphene content, for which the fine-grain strengthening rather than the formation of carbon-rich transfer layer will dominate the lubricating and anti-wear performances.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Liu, Ying and Zheng, Feng and Wu, Yanxia and Koch, Carl C. and Han, Peide and Zhang, Caili and Liu, Yongsheng and Zhang, Yayun}, year={2020}, month={Jun} }
 @article{roy_chakraborty_gupta_mallick_koch_2020, title={Synergistic effect of Nb and Zr addition in thermal stabilization of nano-crystalline Cu synthesized by ball milling}, volume={271}, ISSN={["1873-4979"]}, DOI={10.1016/j.matlet.2020.127780}, abstractNote={Present study concerns strengthening of nanocrystalline Cu-matrix by binary and ternary addition of Zr (0.5 at. %) and Nb (1.0 at. %) using ball milling at cryogenic temperature. Zr and Nb having low equilibrium solid solubility in Cu, thus powder blends were subjected non-equilibrium alloying. Mechanically alloyed samples were annealed at different temperatures (600–900 °C) for one hour. Stability of the nanocrystalline Cu-matrix even after annealing at 900 °C is attributed to the stabilization of nanocrystalline grains by segregation of larger solute atoms (Nb and Zr) along grain boundaries and/or Zener pinning by precipitates like Cu5Zr in Cu-Zr intermetallics.}, journal={MATERIALS LETTERS}, author={Roy, D. and Chakraborty, S. and Gupta, A. K. and Mallick, A. Basu and Koch, Carl C.}, year={2020}, month={Jul} }
 @article{roy_chakraborty_gupta_basumallick_scattergood_koch_2021, title={Synergistic effect of Nb and Zr additions on the structure-property relationships of nanocrystalline Cu processed by mechanical alloying and hot pressing}, volume={854}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2020.157174}, abstractNote={In the present study, bulk nanocrystallineCu99.5Zr0.5, Cu99Nb1.0, and Cu98.5Zr0.5Nb1.0alloys have been synthesized by using mechanical alloying followed by hot pressing (HP) at 550 °C. Further, these as-fabricated alloys were annealed at 800 °C and 900 °C for 1 h to investigate the structure-property correlation. Grain size and phase identification has been carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). While mechanical properties were investigated using Vickers hardness and shear punch test (SPT). The grain size of the as-processed alloys was found to remain nanosized 41 ± 2.2 nm in Cu99.5Zr0.5(CZ), 50 ± 1.5 nm in Cu99Nb1.0(CN) and 26 ± 1.2 nm in Cu98.5Zr0.5Nb1.0 (CNZ) even after annealing at 900 °C. This is attributed to the stabilization of the nanosize grains by segregation of solute atoms (Nb and Zr) along grain boundaries and/or Zenner pinning by intermetallic precipitates like Cu5Zr in CZ and CNZ alloys.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Roy, D. and Chakraborty, S. and Gupta, A. K. and BasuMallick, A. and Scattergood, R. O. and Koch, Carl C.}, year={2021}, month={Feb} }
 @article{muthaiah_koch_mula_2021, title={Thermal stability and mechanical properties of Fe-Cr-Zr alloys developed by mechanical alloying followed by spark plasma sintering}, volume={856}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2020.158266}, abstractNote={The present work aims to investigate (i) the feasibility of formation of Fe-7Cr-xZr and Fe-15Cr-xZr (x = 0.25, 0.5 and 1 at%) disordered solid solutions by mechanical alloying (MA) and (ii) their thermal stability and mechanical properties of spark plasma sintered (SPSed) samples. Effect of Zr addition on phase evolution in Fe-Cr-Zr alloy and its influence on their thermal stability and mechanical properties (microhardness and compression strength) have been studied in detail. Transmission electron microscopy-selected area diffraction pattern (TEM-SAED) and X-ray diffraction (XRD) phase analysis confirm the formation of complete solid solution after 25 h of MA. Grain size was observed to stabilize significantly within nanometer range after annealing at 600–1200 °C. The SPSed (at 1000 °C) samples showed the best combination of hardness (9.4 GPa) and compressive strength (ultimate compressive strength-2200 MPa and yield strength-1800 MPa) corresponding to an average grain size of<100 nm. This is due to the strengthening mechanisms of grain boundary strengthening (owing to solute segregation and solute drag effect), precipitation hardening (Zener pinning) by Fe2Zr phase and excellent densification achieved by SPS.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Muthaiah, V. M. Suntharavel and Koch, Carl C. and Mula, Suhrit}, year={2021}, month={Mar} }
 @article{li_fang_wang_jiang_wang_liu_wu_zhu_koch_2020, title={Tuning heterostructures with powder metallurgy for high synergistic strengthening and hetero-deformation induced hardening}, volume={777}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2020.139074}, abstractNote={Heterogeneous-lamella-structured Fe-Cu composites were fabricated using powder metallurgy, displaying an inverse “banana” curve between the strength and ductility. The density of domain interfaces and the strength difference between hard and soft domains can be tuned independently, providing a promising way to further study the hetero-deformation induced strengthening mechanisms of heterogeneous-lamella-structures.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Li, Z. K. and Fang, X. T. and Wang, Y. F. and Jiang, P. and Wang, J. J. and Liu, C. M. and Wu, X. L. and Zhu, Y. T. and Koch, C. C.}, year={2020}, month={Mar} }
 @article{ma_li_sun_hou_fang_zhu_koch_2019, title={Achieving Gradient Martensite Structure and Enhanced Mechanical Properties in a Metastable beta Titanium Alloy}, volume={50A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-019-05157-5}, number={5}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Ma, Xinkai and Li, Fuguo and Sun, Zhankun and Hou, Junhua and Fang, Xiaotian and Zhu, Yuntian and Koch, Carl C.}, year={2019}, month={May}, pages={2126–2138} }
 @article{sikdar_mahata_chakravarty_atwater_roy_koch_2019, title={Effect of B on the thermal stabilization of cryomilled nanocrystalline Cu–Al alloy}, volume={5}, ISSN={2589-1529}, url={http://dx.doi.org/10.1016/J.MTLA.2019.100253}, DOI={10.1016/J.MTLA.2019.100253}, abstractNote={Nanocrystalline Cu86Al12B2 alloy with an as-milled average grain size of ∼11 nm was synthesized by high-energy ball milling at cryogenic temperature. The alloy was then annealed up to 900 °C (or 0.87 Tm of Cu). Microstructural changes with annealing were assessed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and microindentation. TEM investigation indicates that the newly-developed alloy retains its nanoscale grain size after annealing at 900 °C. The present investigation complements our previous findings of the thermal stability of cryomilled binary Cu88Al12 and Cu86Al14 alloys, where excellent thermal stability was observed and attributed to the in-situ formation of nanoscale Cu–Al precipitates and their Zener pinning effect. First principle calculation shows equilibrium in Al–Cu–B prefers segregation of B in the grain boundary of Cu–Al alloy. Superior thermal stability of the Cu86Al12B2 alloy was primarily ascribed to the synergistic grain boundary pinning of CuAl2 and AlB12 intermetallic phases. Moreover, the alloy maintains a higher hardness than both Cu88Al12 and Cu86Al14 alloy. The grain size dependent Hall–Petch strengthening was found to be the dominant mechanism with substantial contributions from solid solution strengthening and Orowan strengthening in annealed state.}, journal={Materialia}, publisher={Elsevier BV}, author={Sikdar, Koushik and Mahata, Avik and Chakravarty, Somraj and Atwater, Mark A. and Roy, Debdas and Koch, Carl C.}, year={2019}, month={Mar}, pages={100253} }
 @article{koch_langdon_lavernia_2017, title={Bulk Nanostructured Materials}, volume={48A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-017-4298-0}, abstractNote={This paper will address three topics of importance to bulk nanostructured materials. Bulk nanostructured materials are defined as bulk solids with nanoscale or partly nanoscale microstructures. This category of nanostructured materials has historical roots going back many decades but has relatively recent focus due to new discoveries of unique properties of some nanoscale materials. Bulk nanostructured materials are prepared by a variety of severe plastic deformation methods, and these will be reviewed. Powder processing to prepare bulk nanostructured materials requires that the powders be consolidated by typical combinations of pressure and temperature, the latter leading to coarsening of the microstructure. The thermal stability of nanostructured materials will also be discussed. An example of bringing nanostructured materials to applications as structural materials will be described in terms of the cryomilling of powders and their consolidation.}, number={11}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Koch, C. C. and Langdon, T. G. and Lavernia, E. J.}, year={2017}, month={Nov}, pages={5181–5199} }
 @article{roodposhti_saber_koch_scattergood_shahbazmohamadi_2017, title={Effect of oxygen content on thermal stability of grain size for nanocrystalline Fe10Cr and Fe14Cr4Hf alloy powders}, volume={720}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2017.05.261}, abstractNote={Low oxygen content powders of high purity elemental Fe, Cr and Hf were produced in a glove box by mechanically filing the solid materials. Fe10Cr and Fe14Cr4Hf nanocrystalline alloy powders were processed using these elemental powders in conjunction with SPEX ball milling. The grain-size stability of the nanocrystalline alloy powders was investigated for selected annealing temperatures. High temperature stabilization can be achieved by Zener pinning (kinetic mechanism) or segregation of Hf to grain boundaries (thermodynamic mechanism). Solute drag mechanisms can be effective at lower annealing temperatures. Recent regular solution models developed by the authors predict that Hf would facilitate thermodynamic grain-size stabilization in Fe14Cr4Hf alloys at high temperatures. However Hf-base reactions such as intermetallic phase or oxide formation can favor kinetic stabilization and this can dominate over a contribution from thermodynamic stabilization. In contrast, grain-size stabilization in Fe10Cr alloy would be a result of solute drag by the Cr solutes at lower temperatures. The results from previous investigations on Fe10Cr and Fe14Cr4Hf nanocrystalline alloys were (unknowingly at the time) influenced by the fact that the commercially available high purity elemental powders used for SPEX ball mill processing contained significant amounts of oxygen impurity. The results obtained in this investigation using identical processing methods with low oxygen content powders for synthesizing the alloys provide further insight into their stabilization mechanisms.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Roodposhti, Peiman Shahbeigi and Saber, Mostafa and Koch, Carl and Scattergood, Ronald and Shahbazmohamadi, Sina}, year={2017}, month={Oct}, pages={510–520} }
 @article{chakravarty_sikdar_singh_roy_koch_2017, title={Grain size stabilization and strengthening of cryomilled nanostructured Cu 12 at% Al alloy}, volume={716}, ISSN={0925-8388}, url={http://dx.doi.org/10.1016/J.JALLCOM.2017.05.093}, DOI={10.1016/J.JALLCOM.2017.05.093}, abstractNote={Nanocrystalline Cu12 at% Al alloy was synthesized by high energy ball milling under cryogenic condition. The alloy was then annealed up to 900 °C (or 0.87 Tm). Phase and microstructural evaluation were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM) and the mechanical property was investigated by microhardness testing. Results show that at elevated temperatures grain growth of Cu 12 at% Al alloy is much less than pure Cu prepared under same condition. The microhardness of the alloy decreases from 2.91 GPa to 2.73 GPa (∼6% decrease) after annealing at 900 °C. Superior thermal stability at high temperature was ascribed to the grain boundary pinning by nano-scale intermetallic particles. Kinetically stabilized grain size and hardness show good agreement with theoretical predictions.}, journal={Journal of Alloys and Compounds}, publisher={Elsevier BV}, author={Chakravarty, Somraj and Sikdar, Koushik and Singh, Shudhansu S. and Roy, Debdas and Koch, Carl C.}, year={2017}, month={Sep}, pages={197–203} }
 @article{youssef_abaza_scattergood_koch_2018, title={High strength, ductility, and electrical conductivity of in-situ consolidated nanocrystalline Cu-1%Nb}, volume={711}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2017.11.060}, abstractNote={Nanocrystalline metals—with grain sizes less than 100 nm— have strengths exceeding those of coarse-grained and even alloyed metals [1], [2]. A bulk nanocrystalline Cu-1%Nb alloy was synthesized by an in-situ consolidation mechanical alloying technique. The mechanical behavior of this alloy was investigated by hardness and tensile tests. The nanostructure was investigated by X-ray diffraction and transmission electron microscopy and the fracture surface by scanning electron microscopy. Electrical resistivity was measured using a four-point probe technique. The dilute additives of Nb and the processing conditions induced artifact-free bulk nanocrystalline materials that possess extraordinary high strength, good ductility, and high electrical conductivity.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Youssef, Khaled M. and Abaza, Mohamed A. and Scattergood, Ronald O. and Koch, Carl C.}, year={2018}, month={Jan}, pages={350–355} }
 @misc{koch_2017, title={Nanocrystalline high-entropy alloys}, volume={32}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2017.341}, abstractNote={Abstract}, number={18}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Koch, Carl C.}, year={2017}, month={Sep}, pages={3435–3444} }
 @article{xu_zhang_cheng_mathaudhu_scattergood_koch_lavernia_zhu_2017, title={On the origin and behavior of irradiation-induced c-component dislocation loops in magnesium}, volume={131}, ISSN={["1873-2453"]}, url={https://doi.org/10.1016/j.actamat.2017.04.015}, DOI={10.1016/j.actamat.2017.04.015}, abstractNote={C-component dislocation loops are one of the unique defects in hexagonal close-packed (hcp) crystals that promote the accelerated growth and void formation under irradiation. Here, we report in situ observation of c-component dislocation loop formation in Mg under electron irradiation with emphasis on their atomic structures. Aberration-corrected scanning transmission electron microscopy imaging is utilized to reveal four possible types of double-layer loops, which were identified as different types of stacking fault and dislocation core structures. Triple- and quadruple-layer c-component dislocation loops were also observed. The formation mechanisms of the four types of double-layer loops were revealed via molecular dynamics simulations. The experimentally observed formation rate of the single- and double-layer dislocation loops is controlled by their formation energies. Our direct experimental observations in combination with molecular dynamics simulations provide fundamental insight into the mechanisms governing nucleation and growth of the c-component dislocation loops as well as their interactions, which could potentially help with future development of irradiation-resistant materials.}, journal={ACTA MATERIALIA}, publisher={Elsevier BV}, author={Xu, Weizong and Zhang, Yongfeng and Cheng, Guangming and Mathaudhu, Suveen N. and Scattergood, Ronald O. and Koch, Carl C. and Lavernia, Enrique J. and Zhu, Yuntian}, year={2017}, month={Jun}, pages={457–466} }
 @article{jha_dulikravich_chakraborti_fan_schwartz_koch_colaco_poloni_egorov_2017, title={Self-organizing maps for pattern recognition in design of alloys}, volume={32}, ISSN={["1532-2475"]}, DOI={10.1080/10426914.2017.1279319}, abstractNote={ABSTRACT A combined experimental–computational methodology for accelerated design of AlNiCo-type permanent magnetic alloys is presented with the objective of simultaneously extremizing several magnetic properties. Chemical concentrations of eight alloying elements were initially generated using a quasi-random number generator so as to achieve a uniform distribution in the design variable space. It was followed by manufacture and experimental evaluation of these alloys using an identical thermo-magnetic protocol. These experimental data were used to develop meta-models capable of directly relating the chemical composition with desired macroscopic properties of the alloys. These properties were simultaneously optimized to predict chemical compositions that result in improvement of properties. These data were further utilized to discover various correlations within the experimental dataset by using several concepts of artificial intelligence. In this work, an unsupervised neural network known as self-organizing maps was used to discover various patterns reported in the literature. These maps were also used to screen the composition of the next set of alloys to be manufactured and tested in the next iterative cycle. Several of these Pareto-optimized predictions out-performed the initial batch of alloys. This approach helps significantly reducing the time and the number of alloys needed in the alloy development process.}, number={10}, journal={MATERIALS AND MANUFACTURING PROCESSES}, author={Jha, Rajesh and Dulikravich, George S. and Chakraborti, Nirupam and Fan, Min and Schwartz, Justin and Koch, Carl C. and Colaco, Marcelo J. and Poloni, Carlo and Egorov, Igor N.}, year={2017}, pages={1067–1074} }
 @article{sikdar_chakravarty_roy_scattergood_koch_2017, title={Synthesis and characterization of an in situ consolidated nanocrystalline Cu88Al11.5Y0.5 alloy}, volume={717}, ISSN={0925-8388}, url={http://dx.doi.org/10.1016/J.JALLCOM.2017.05.092}, DOI={10.1016/J.JALLCOM.2017.05.092}, abstractNote={Artifact-free bulk nanocrystalline Cu88Al11.5Y0.5 alloy has been synthesized by in situ consolidation of mechanically alloyed powder blend followed by annealing of the consolidated compact at 200 °C (or 0.35 Tm) for 30 min. Grain size determination and phase identification have been carried by X-ray line broadening analysis and transmission electron microscopy (TEM). Hardness measurement has demonstrated that the Hall-Petch effect is the dominant strengthening mechanism for both as-consolidated and annealed specimens. Strength improvement after short annealing time was attributed to the relaxations of non-equilibrium grain boundaries.}, journal={Journal of Alloys and Compounds}, publisher={Elsevier BV}, author={Sikdar, Koushik and Chakravarty, Somraj and Roy, Debdas and Scattergood, Ronald O. and Koch, Carl C.}, year={2017}, month={Sep}, pages={219–225} }
 @article{jha_dulikravich_chakraborti_fan_schwartz_koch_colaco_poloni_egorov_2016, title={Algorithms for design optimization of chemistry of hard magnetic alloys using experimental data}, volume={682}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2016.04.218}, abstractNote={A multi-dimensional random number generation algorithm was used to distribute chemical concentrations of each of the alloying elements in the candidate alloys as uniformly as possible while maintaining the prescribed bounds on the minimum and maximum allowable values for the concentration of each of the alloying elements. The generated candidate alloy compositions were then examined for phase equilibria and associated magnetic properties using a thermodynamic database in the desired temperature range. These initial candidate alloys were manufactured, synthesized and tested for desired properties. Then, the experimentally obtained values of the properties were fitted with a multi-dimensional response surface. The desired properties were treated as objectives and were extremized simultaneously by utilizing a multi-objective optimization algorithm that optimized the concentrations of each of the alloying elements. This task was also performed by another conceptually different response surface and optimization algorithm for double-checking the results. A few of the best predicted Pareto optimal alloy compositions were then manufactured, synthesized and tested to evaluate their macroscopic properties. Several of these Pareto optimized alloys outperformed most of the candidate alloys on most of the objectives. This proves the efficacy of the combined meta-modeling and experimental approach in design optimization of the alloys. A sensitivity analysis of each of the alloying elements was also performed to determine which of the alloying elements contributes the least to the desired macroscopic properties of the alloy. These elements can then be replaced with other candidate alloying elements such as not-so-rare earth elements.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Jha, Rajesh and Dulikravich, George S. and Chakraborti, Nirupam and Fan, Min and Schwartz, Justin and Koch, Carl C. and Colaco, Marcelo J. and Poloni, Carlo and Egorov, Igor N.}, year={2016}, month={Oct}, pages={454–467} }
 @article{muthaiah_babu_koch_mula_2016, title={Feasibility of formation of nanocrystalline Fe-Cr-Y alloys: Mechanical properties and thermal stability}, volume={114}, ISSN={1044-5803}, url={http://dx.doi.org/10.1016/J.MATCHAR.2016.02.005}, DOI={10.1016/J.MATCHAR.2016.02.005}, abstractNote={Aim of the present study is to investigate the feasibility of formation of Fe-Cr-Y disordered solid solutions by mechanical alloying and effect of Y on the thermal stability and mechanical properties of such nanocrystalline alloys. Thermodynamic analysis by Miedema's and Toop's models confirms that the energy barrier required to form the disordered solid solutions has been overcome by the stored energy due to strain dislocations and grain boundary defects. Although limited grain growth was observed during annealing of metastable Fe-15Cr-1Y alloy, the grains size found to stabilize at ~ 53 nm after annealing at 1000 °C; and the corresponding hardness value measured to be also quite high (8 GPa). The grain size analysis by TEM and AFM is well-corroborated with the XRD crystallite size. The high thermal stability and large strengthening effect have been discussed in the light of grain boundary pinning by solute segregation, solute drag effect and Zener pinning due to intermetallic phase(s).}, journal={Materials Characterization}, publisher={Elsevier BV}, author={Muthaiah, V.M. Suntharavel and Babu, L. Hari and Koch, Carl C. and Mula, Suhrit}, year={2016}, month={Apr}, pages={43–53} }
 @article{niu_zaddach_koch_irving_2016, title={First principles exploration of near-equiatomic NiFeCrCo high entropy alloys}, volume={672}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2016.02.108}, abstractNote={High entropy alloy NiFeCrCo was systematically studied in the range of near-equal atomic concentrations, i.e., 10–40 at.%, by first-principles tools and high throughput calculations. Enthalpy of mixing, lattice parameter (a0), bulk modulus (B), and shear modulus (G) were calculated by the exact muffin-tin orbital method combined with coherent potential approximation (EMTO-CPA) for over 2700 compositions of the NiFeCrCo alloy as a single-phase solid solution in paramagnetic state. It was found that certain elements have the most significant influence on each property, namely, Cr on enthalpy of mixing, Co on a0, Fe on B, Co on G, and Cr on the ratio of B/G. An equation to predict the enthalpy of mixing by use of binary enthalpy data was evaluated and was found to have a good accuracy with a root-mean-square deviation (RMSD) of 42 meV per formula unit in the prediction. A similar equation to predict bulk modulus with weighted contribution from first–shell interaction is proposed and tested on all alloys. This equation was also found to be accurate with a RMSD of 6 GPa. Finally, it was found that shear moduli of all tested alloys are largely dependent on C44, while the concentration of Co has a noticeable control on C44. Spin polarized calculations were performed for a select group of alloys with both EMTO-CPA and the Vienna ab-initio Simulation Package (VASP) with special quasi-random structure models for comparison. Good agreement was found between these methods.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Niu, C. and Zaddach, A. J. and Koch, C. C. and Irving, D. L.}, year={2016}, month={Jul}, pages={510–520} }
 @article{zhang_koch_schwartz_2016, title={Formation of Bi2Sr2CaCu2Ox/Ag multifilamentary metallic precursor powder-in-tube wires}, volume={29}, ISSN={["1361-6668"]}, DOI={10.1088/0953-2048/29/12/125005}, abstractNote={Previously, a metallic precursor (MP) approach to synthesizing Bi2Sr2CaCu2Ox (Bi2212), with a homogeneous mixture of Bi, Sr, Ca, Cu and Ag was produced by mechanical alloying. Here, Bi2212/Ag round multifilamentary wire is manufactured using a metallic precursor powder-in-tube (MPIT) process. The MP powders were packed into a pure Ag tube in an Ar atmosphere and then sealed. After deformation, multifilamentary round wires and rolled tapes were heat treated in flowing oxygen through three stages: oxidation, conversion and partial-melt processing (PMP). Processing-microstructure-property relationships on 20–50 mm long multifilamentary round wires and rolled tapes were studied extensively. It is shown that conventional wire deformation processes, optimized for oxide-powder-in-tube wires, are not effective for deforming MPIT wires, and that as with prior studies of MPIT Bi2Sr2Ca2Cu3Oy conductors, hot extrusion is required for obtaining a multifilamentary structure with fine filaments. As a result, the Bi2212 MPIT wires reported here have low engineering critical current density. Nonetheless, by focusing on sections of wires that remain intact after deformation, it is also shown that the first heat treatment stage, the oxidation stage, plays a crucial role in chemical homogeneity, phase transformation, and microstructural evolution and three reaction pathways for MP oxidation are presented. Furthermore, it is found the Bi2212 grain alignment within an MPIT filament is significantly different from that found in OPIT filaments after PMP, indicating the formation of highly dense filaments containing Bi2212 fine grains and Ag particles before PMP aids the formation of large, c-axis textured Bi2212 filaments during PMP. These results show that, with improved wire deformation, high critical current density may be obtained via a MPIT process.}, number={12}, journal={SUPERCONDUCTOR SCIENCE & TECHNOLOGY}, author={Zhang, Yun and Koch, Carl C. and Schwartz, Justin}, year={2016}, month={Dec} }
 @article{sooraj_muthaiah_kang_koch_mula_2016, title={Microstructural evolution and thermal stability of Fe–Zr metastable alloys developed by mechanical alloying followed by annealing}, volume={96}, ISSN={1478-6435 1478-6443}, url={http://dx.doi.org/10.1080/14786435.2016.1212173}, DOI={10.1080/14786435.2016.1212173}, abstractNote={Abstract The effect of Zr (up to 1 at.%) addition on the formation of Fe–Zr metastable alloys and their thermal stability were investigated for their possible nuclear applications. Fe–xZr (x = 0.25, 0.5, 1%) alloys were synthesised by mechanical alloying under a high-purity argon atmosphere using stainless steel grinding media in a SPEX 8000M high energy mill. The milling was conducted for 20 h with a ball-to-powder weight ratio of 10:1. The formation of metastable solid solutions after milling was confirmed from the change in the Gibbs free energy analysis as per Miedema’s model. The microstructural characterisation was carried out by analysis of X-ray diffraction, atomic force microscopy and transmission electron microscopy. The effect of Zr on the thermal stability of Fe–Zr alloys was investigated by extensive annealing experiments followed by microstructural analysis and microhardness measurements. The stabilisation was found to occur at 800 °C and thereafter, no significant change in the crystallite size was observed for the samples annealed between 800 and 1200 °C. The supersaturated solid solution, especially 1% Zr alloy, found to be highly stable up to 800 °C and the microhardness value of the same measured to be as high as 8.8 GPa corresponding to a crystallite size of 57 nm. The stabilisation effect has been discussed in the light of both the thermodynamic and kinetic mechanisms and the grain size stabilisation is attributed to the grain boundary segregation of Zr atoms and/or Zener pinning by nanoscale precipitation of the Fe2Zr phase.}, number={25}, journal={Philosophical Magazine}, publisher={Informa UK Limited}, author={Sooraj, S. and Muthaiah, V. M. Suntharavel and Kang, P. C. and Koch, Carl C. and Mula, Suhrit}, year={2016}, month={Jul}, pages={2649–2670} }
 @article{fan_liu_jha_dulikravich_schwartz_koch_2016, title={On the Formation and Evolution of Cu-Ni-Rich Bridges of Alnico Alloys With Thermomagnetic Treatment}, volume={52}, ISSN={["1941-0069"]}, DOI={10.1109/tmag.2016.2555956}, abstractNote={Despite decades of research and development of Alnico alloys, significant uncertainties in the underlying structure-property relationships remain. Here, we report on the effects of Ti on the Alnico microstructure and nanostructure, and the corresponding influence on magnetic properties. We show that Ti fosters the conditions resulting in the formation of Cu-Ni-rich bridges in the α1 phases between the α2 phases. For Alnico containing Ti, a typical chessboardlike morphology with Cu-Ni-rich bridges is observed, whereas in the absence of Ti, the α1 phases connect to each other readily, especially with a high Co concentration, and a mazelike morphology with Cu-rich white-plate precipitates rather than Cu-rich bridges is observed. Furthermore, in Alnico containing Ti, an inhomogeneous distribution of Ni is found in the α2 phases, including loops with high Ni concentration surrounding the α1 phase and high concentrations in the bridges as well. An increase in the Cu concentration is also observed in the loops around the α1 phases (Ni-Cu loops), and direct contact between the Cu-Ni-rich bridges and the Ni-Cu loops is observed in lieu of direct contact between the bridges and the α1 phases. We also observe that the bridges are not perfectly round but ellipsoidal, with the long axis along the connection of two adjacent α1 phases. The energy-dispersive X-ray spectroscopy line scans of the bridges shows that two types of Cu-Ni-rich bridges exist: those with more Cu than Ni and those with more Ni than Cu. A 3-D model is presented that explains the conditions and process of bridge formation, consistent with the observed composition distributions.}, number={8}, journal={IEEE TRANSACTIONS ON MAGNETICS}, author={Fan, M. and Liu, Y. and Jha, Rajesh and Dulikravich, George S. and Schwartz, J. and Koch, C. C.}, year={2016}, month={Aug} }
 @article{fan_liu_jha_dulikravich_schwartz_koch_2016, title={On the evolution of Cu-Ni-rich bridges of Alnico alloys with tempering}, volume={420}, ISSN={["1873-4766"]}, DOI={10.1016/j.jmmm.2016.07.040}, abstractNote={Tempering is a critical step in Alnico alloy processing, yet the effects of tempering on microstructure have not been well studied. Here we report these effects, and in particular the effects on the Cu-Ni bridges. Energy-dispersive X-ray spectroscopy (EDS) maps and line scans show that tempering changes the elemental distribution in the Cu-Ni bridges, but not the morphology and distribution of Cu-bridges. The Cu concentration in the Cu-Ni bridges increases after tempering while other element concentrations decrease, especially Ni and Al. Furthermore, tempering sharpens the Cu bridge boundaries. These effects are primarily related to the large 2C44/(C11−C12) ratio for Cu, largest of all elements in Alnico. In addition, the Ni-Cu loops around the α1 phases become inconspicuous with tempering. The diffusion of Fe and Co to the α1 phase during tempering, which increases the difference of saturation magnetization between the α1 and α2 phases, is observed by EDS. In summary, α1, α2 and Cu-bridges are concentrated with their major elements during tempering which improves the magnetic properties. The formation of these features formed through elemental diffusion is discussed via energy theories.}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Fan, M. and Liu, Y. and Jha, Rajesh and Dulikravich, George S. and Schwartz, J. and Koch, C. C.}, year={2016}, month={Dec}, pages={296–302} }
 @article{dwivedi_koch_rajulapati_2016, title={On the single phase fcc solid solution in nanocrystalline Cr-Nb-Ti-V-Zn high-entropy alloy}, volume={183}, ISSN={["1873-4979"]}, DOI={10.1016/j.matlet.2016.07.083}, abstractNote={A single phase fcc solid solution, with a lattice parameter of 4.20±0.01 Å and a crystallite size of 7±2 nm (TEM), has been observed in an equiatomic nanocrystalline Cr-Nb-Ti-V-Zn high-entropy alloy during mechanical alloying. Uniqueness of this work is that an fcc solid solution was observed in a system where none of the elements is fcc. This system obeys the guiding principles laid down for high entropy alloys based on atomic size difference, ΔHmix and ΔSmix. However it does not obey the guidelines based on valence electron concentration.}, journal={MATERIALS LETTERS}, author={Dwivedi, Akanksha and Koch, Carl C. and Rajulapati, Koteswararao V.}, year={2016}, month={Nov}, pages={44–47} }
 @article{mahesh_singh raman_scattergood_koch_2016, title={Retraction notice to “Fe–Cr–Ni–Zr alloys with bi-modal grain size distribution: Synthesis, mechanical properties and oxidation resistance” [Mater. Sci. Eng. A 574 (2013) 235–242]}, volume={660}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/J.MSEA.2016.03.003}, DOI={10.1016/J.MSEA.2016.03.003}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Mahesh, B.V. and Singh Raman, R.K. and Scattergood, R.O. and Koch, C.C.}, year={2016}, month={Apr}, pages={251} }
 @article{dycus_harris_sang_fancher_findlay_oni_chan_koch_jones_allen_et al._2015, title={Accurate Nanoscale Crystallography in Real-Space Using Scanning Transmission Electron Microscopy}, volume={21}, ISSN={["1435-8115"]}, url={http://dx.doi.org/10.1017/s1431927615013732}, DOI={10.1017/s1431927615013732}, abstractNote={AbstractHere, we report reproducible and accurate measurement of crystallographic parameters using scanning transmission electron microscopy. This is made possible by removing drift and residual scan distortion. We demonstrate real-space lattice parameter measurements with <0.1% error for complex-layered chalcogenides Bi2Te3, Bi2Se3, and a Bi2Te2.7Se0.3 nanostructured alloy. Pairing the technique with atomic resolution spectroscopy, we connect local structure with chemistry and bonding. Combining these results with density functional theory, we show that the incorporation of Se into Bi2Te3 causes charge redistribution that anomalously increases the van der Waals gap between building blocks of the layered structure. The results show that atomic resolution imaging with electrons can accurately and robustly quantify crystallography at the nanoscale.}, number={4}, journal={MICROSCOPY AND MICROANALYSIS}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. Houston and Harris, Joshua S. and Sang, Xiahan and Fancher, Chris M. and Findlay, Scott D. and Oni, Adedapo A. and Chan, Tsung-ta E. and Koch, Carl C. and Jones, Jacob L. and Allen, Leslie J. and et al.}, year={2015}, month={Aug}, pages={946–952} }
 @article{xu_li_valdez_saber_zhu_koch_scattergood_2016, title={Effect of nano-oxide particle size on radiation resistance of iron-chromium alloys}, volume={469}, ISSN={["1873-4820"]}, DOI={10.1016/j.jnucmat.2015.11.044}, abstractNote={Radiation resistance of Fe–14Cr alloys under 200 keV He irradiation at 500 °C was systematically investigated with varying sizes of nano oxide Zr, Hf and Cr particles. It is found that these nano oxide particles acted as effective sites for He bubble formation. By statistically analyzing 700–1500 He bubbles at the depth of about 150–700 nm from a series of HRTEM images for each sample, we established the variation of average He bubble size, He bubble density, and swelling percentage along the depth, and found them to be consistent with the He concentration profile calculated from the SIRM program. Oxide particles with sizes less than 3.5–4 nm are found most effective for enhancing radiation resistance in the studied alloy systems.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Xu, Weizong and Li, Lulu and Valdez, James A. and Saber, Mostafa and Zhu, Yuntian and Koch, Carl C. and Scattergood, Ronald O.}, year={2016}, month={Feb}, pages={72–81} }
 @article{dasharath_koch_mula_2015, title={Effect of stacking fault energy on mechanical properties and,strengthening mechanisms of brasses processed by cryorolling}, volume={110}, ISSN={["1873-4189"]}, DOI={10.1016/j.matchar.2015.10.006}, abstractNote={In the present study, contribution of individual strengthening mechanisms has been analyzed to corroborate the improvement of the mechanical properties of cryorolled brasses of Cu–3.8% Zn and Cu–9.6%1 Zn compositions. The samples were cryorolled up to the maximum possible reduction in area after homogenized annealing (at 800 °C for 4 h). After the cryodeformation, a remarkable ~ 12 times improvement of yield strength (YS) was observed for both the alloys compared to that of the homogenized samples. The improvement of the YS is found to be much higher compared to that reported in our earlier work [Mater. Des 67 (2015) 637–643], although alloying content is much less in the present study. This is attributed to the change in rolling design, which allowed deformation of the samples under LN2 during rolling. The short time ageing (20 min, 225–300 °C) followed by cryorolling was found to enhance ductility without affecting the YS significantly. The solid solution strengthening by Zn in Cu leads to the decrease in the stacking fault energy which prevents the dynamic recovery and restricts the process of cross slip. Thereby, it helps to increase twining activity for further deformation. The TEM investigation confirmed that the formation of subgrains and nanotwins is responsible for the simultaneous improvement of strength and ductility. The analysis of different strengthening mechanisms revealed that the grain size refinement played the pivotal role in the improvement of the mechanical properties.}, journal={MATERIALS CHARACTERIZATION}, author={Dasharath, S. M. and Koch, Carl C. and Mula, Suhrit}, year={2015}, month={Dec}, pages={14–24} }
 @article{cook_chan_dezsi_thomas_koch_poon_tritt_venkatasubramanian_2015, title={High-Performance Three-Stage Cascade Thermoelectric Devices with 20% Efficiency}, volume={44}, ISSN={["1543-186X"]}, DOI={10.1007/s11664-014-3600-9}, number={6}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Cook, B. A. and Chan, T. E. and Dezsi, G. and Thomas, P. and Koch, C. C. and Poon, J. and Tritt, T. and Venkatasubramanian, R.}, year={2015}, month={Jun}, pages={1936–1942} }
 @article{dycus_harris_sang_fancher_findlay_oni_chan_koch_jones_allen_et al._2015, title={Highly Accurate Real Space Nanometrology Using Revolving Scanning Transmission Electron Microscopy}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615012003}, DOI={10.1017/S1431927615012003}, abstractNote={, Accurately determining crystallography at the nanoscale provides key understanding of materials behavior. X-ray and neutron based diffraction methods provide highly accurate and precise measurements, but are typically limited in their application for nanoscale materials by poor spatial sensitivity. On the other hand, scanning transmission electron microscopy (STEM) is capable of spatial resolutions below an angstrom, making atomic scale analysis routine. Moreover, high-angle annular dark-field STEM produces images that are directly interpretable with intensities scaling to the atomic number and total number of atoms in a column [1-2]. While, real-space distance measurements are possible with STEM, the effects of thermal drift and scan distortion hinder accurate metrology. In this talk, we will combine revolving STEM (RevSTEM) with a method for scan distortion correction to show accurate and precise real space length measurements for a nanostructured Bi 2 Te 3-x Se x alloy. We will show the effects of thermal drift can be corrected via measuring the drift parameters from multiple frames in an image series [3]. B y using <100> silicon as a reference standard, we correct the effects from distortions introduced from the scan system, which can then be used for imaging samples of unknown crystallography. The atom columns in drift corrected image series are then indexed and assigned to a matrix representation, which yields information such as the lattice parameters on a unit cell-by-unit cell basis, shown in Figure 1a [4]. To validate the accuracy of the technique, samples of pure Bi 2 Te 3 and Bi 2 Se}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. H. and Harris, J. S. and Sang, X. and Fancher, C. M. and Findlay, S. D. and Oni, A. A. and Chan, T. E. and Koch, C. C. and Jones, J. L. and Allen, L. J. and et al.}, year={2015}, month={Aug}, pages={2245–2246} }
 @article{li_xu_saber_zhu_koch_scattergood_2015, title={Influence of scandium addition on the high-temperature grain size stabilization of oxide-dispersion-strengthened (ODS) ferritic alloy}, volume={636}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2015.03.117}, abstractNote={The influence of 1–4 at% Sc addition on the thermal stability of mechanically alloyed ODS ferritic alloy was studied in this work. Sc addition was found to significantly stabilize grain size and microhardness at high temperatures. Grain sizes of samples with 1 and 4 at% Sc was found maintained in the nanoscale range at temperatures up to 1000 °C with hardness maintained at 5.6 and 6.7 GPa, respectively. The detailed microstructure was also investigated from EDS elemental mapping, where nanofeatures [ScTiO] were observed, while nanosized [YTiO] particles were rarely seen. This is probably due to the concentration difference between Sc and Y, leading to the formation of [ScTiO] favoring that of [YTiO]. Precipitation was considered as the major source for the observed high temperature stabilization. In addition, 14YT–Sc alloys without large second phases such as Ti-oxide can exhibit better performance compared to conventional ODS materials.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Li, Lulu and Xu, Weizong and Saber, Mostafa and Zhu, Yuntian and Koch, Carl C. and Scattergood, Ronald O.}, year={2015}, month={Jun}, pages={565–571} }
 @article{li_xu_saber_zhu_koch_scattergood_2015, title={Long-term stability of 14YT-4Sc alloy at high temperature}, volume={647}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2015.09.012}, abstractNote={14YT alloy (Fe–14Cr–0.25wt%Y2O3–0.4wt%Ti) with 4 at% Sc addition was previously reported to exhibit a nanoscale microstructure and high strength when annealed at temperatures up to 1000 °C (0.65Tm) for 1 h. Here we report that the microstructure and mechanical behavior of 14YT–4Sc alloy after long-term annealing for up to 60 h at 1000 °C. FIB analysis shows abnormal grain growth with annealing time, while a large fraction of the matrix still consists of nanoscale grains. TEM images reveal a slight growth of nano grains, with estimated grain growth exponent, n, to be 0.29. Sc–Ti–Y–O enriched nano oxide particles (<10 nm) were observed in EDS mapping of the 14YT–4Sc–60h sample. The nano-structure retention at the high temperature of 1000 °C for 60 h is attributed to these complex nano oxides.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Li, Lulu and Xu, Weizong and Saber, Mostafa and Zhu, Yuntian and Koch, Carl C. and Scattergood, Ronald O.}, year={2015}, month={Oct}, pages={222–228} }
 @article{xu_li_saber_koch_zhu_scattergood_2015, title={Microstructures and Stabilization Mechanisms of Nanocrystalline Iron-Chromium Alloys with Hafnium Addition}, volume={46A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-015-2985-2}, number={9}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Xu, Weizong and Li, Lulu and Saber, Mostafa and Koch, Carl C. and Zhu, Yuntian and Scattergood, Ronald O.}, year={2015}, month={Sep}, pages={4394–4404} }
 @article{mahesh_raman_koch_2015, title={Resistance of Nanostructured Fe-Cr Alloys to Oxidative Degradation: Role of Zr and Cr Contents}, volume={46A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-015-2765-z}, number={4}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Mahesh, B. V. and Raman, R. K. Singh and Koch, C. C.}, year={2015}, month={Apr}, pages={1814–1824} }
 @article{niu_zaddach_oni_sang_hurt_lebeau_koch_irving_2015, title={Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo}, volume={106}, ISSN={["1077-3118"]}, DOI={10.1063/1.4918996}, abstractNote={Spin-driven ordering of Cr in an equiatomic fcc NiFeCrCo high entropy alloy (HEA) was predicted by first-principles calculations. Ordering of Cr is driven by the reduction in energy realized by surrounding anti-ferromagnetic Cr with ferromagnetic Ni, Fe, and Co in an alloyed L12 structure. The fully Cr-ordered alloyed L12 phase was predicted to have a magnetic moment that is 36% of that for the magnetically frustrated random solid solution. Three samples were synthesized by milling or casting/annealing. The cast/annealed sample was found to have a low temperature magnetic moment that is 44% of the moment in the milled sample, which is consistent with theoretical predictions for ordering. Scanning transmission electron microscopy measurements were performed and the presence of ordered nano-domains in cast/annealed samples throughout the equiatomic NiFeCrCo HEA was identified.}, number={16}, journal={APPLIED PHYSICS LETTERS}, author={Niu, C. and Zaddach, A. J. and Oni, A. A. and Sang, X. and Hurt, J. W., III and LeBeau, J. M. and Koch, C. C. and Irving, D. L.}, year={2015}, month={Apr} }
 @article{zaddach_niu_oni_fan_lebeau_irving_koch_2016, title={Structure and magnetic properties of a multi-principal element Ni-Fe-Cr-Co-Zn-Mn alloy}, volume={68}, ISSN={["1879-0216"]}, DOI={10.1016/j.intermet.2015.09.009}, abstractNote={A nanocrystalline alloy with a nominal composition of Ni20Fe20Cr20Co20Zn15Mn5 was produced by mechanical alloying and processed using annealing treatments between 450 and 600 °C for lengths from 0.5 to 4 h. Analysis was conducted using x-ray diffraction, transmission electron microscopy, magnetometry, and first-principles calculations. Despite designing the alloy using empirical high-entropy alloy guidelines, it was found to precipitate numerous phases after annealing. These precipitates included a magnetic phase, α-FeCo, which, after the optimal heat treatment conditions of 1 h at 500 °C, resulted in an alloy with reasonably good hard magnetic properties. The effect of annealing temperature and time on the microstructure and magnetic properties are discussed, as well as the likely mechanisms that cause the microstructure development.}, journal={INTERMETALLICS}, author={Zaddach, A. J. and Niu, C. and Oni, A. A. and Fan, M. and LeBeau, J. M. and Irving, D. L. and Koch, C. C.}, year={2016}, month={Jan}, pages={107–112} }
 @article{zaddach_scattergood_koch_2015, title={Tensile properties of low-stacking fault energy high-entropy alloys}, volume={636}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2015.03.109}, abstractNote={An equiatomic NiFeCrCoMn alloy, two non-equiatomic NiFeCrCoMn alloys optimized for low stacking fault energy, and an equiatomic NiFeCrCo alloy were produced by arc melting. Samples were homogenized, cold rolled, and annealed at temperatures between 575 and 1100 °C. Samples annealed at a moderate temperature near their recrystallization temperature (625–675 °C) and 1100 °C were cut into flat tensile samples and tested at a strain rate of 7.3×10−4 s−1. Equiatomic NiFeCrCo had the highest ductility and toughness after annealing at both temperatures, followed by Ni18.5Fe18.5Cr18.5Co26Mn18.5. Ni14Fe20Cr26Co20Mn20 exhibited poor thermal stability, forming σ-phase intermetallics at temperatures below 1100 °C. Observation of the fracture surfaces suggested that the high performance of NiFeCrCo might be due to the absence of oxide particles that form in the Mn-containing alloys. The strain-hardening rate and exponent were calculated from the results, showing a large deviation from typical behavior and significant grain size dependence.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Zaddach, A. J. and Scattergood, R. O. and Koch, C. C.}, year={2015}, month={Jun}, pages={373–378} }
 @article{saber_koch_scattergood_2015, title={Thermodynamic Grain Size Stabilization Models: An Overview}, volume={3}, ISSN={["2166-3831"]}, DOI={10.1080/21663831.2014.997894}, abstractNote={Grain boundaries in a nanocrystalline microstructure produce an increase in the excess free energy of the system. Grain growth is a consequence of the thermodynamic driving force reducing this excess. Thermodynamic stabilization is an approach based on eliminating the driving force by suitable alloy additions that can produce a metastable equilibrium state at the nanoscale grain size, as opposed to kinetic stabilization where the grain growth mobility is restricted by pinning and/or drag mechanisms. The present paper reviews and compares various models proposed for thermodynamic stabilization.}, number={2}, journal={MATERIALS RESEARCH LETTERS}, author={Saber, Mostafa and Koch, Carl C. and Scattergood, Ronald O.}, year={2015}, pages={65–75} }
 @article{youssef_zaddach_niu_irving_koch_2015, title={A Novel Low-Density, High-Hardness, High-entropy Alloy with Close-packed Single-phase Nanocrystalline Structures}, volume={3}, ISSN={["2166-3831"]}, DOI={10.1080/21663831.2014.985855}, abstractNote={A low-density, nanocrystalline high-entropy alloy, Al20Li20Mg10Sc20Ti30 was produced by mechanical alloying. It formed a single-phase fcc structure during ball milling and transformed to single-phase hcp upon annealing. The alloy has an estimated strength-to-weight ratio that is significantly higher than other nanocrystalline alloys and is comparable to ceramics. High hardness is retained after annealing.}, number={2}, journal={MATERIALS RESEARCH LETTERS}, author={Youssef, Khaled M. and Zaddach, Alexander J. and Niu, Changning and Irving, Douglas L. and Koch, Carl C.}, year={2015}, pages={95–99} }
 @article{xu_zhang_cheng_jian_millett_koch_mathaudhu_zhu_2014, title={Dynamic Void Growth and Shrinkage in Mg under Electron Irradiation}, volume={2}, ISSN={2166-3831}, url={http://dx.doi.org/10.1080/21663831.2014.904826}, DOI={10.1080/21663831.2014.904826}, abstractNote={We report in situ atomic-scale investigation of late-stage void evolution, including growth, coalescence and shrinkage, under electron irradiation. With increasing irradiation dose, the total volume of voids increased linearly, while the nucleation rate of new voids decreased slightly and the total number of voids decreased. Some voids continued to grow while others shrank to disappear, depending on the nature of their interactions with nearby self-interstitial loops. For the first time, surface diffusion of adatoms was observed to be largely responsible for the void coalescence and thickening. These findings provide fundamental understanding to help with the design and modeling of irradiation-resistant materials.}, number={3}, journal={Materials Research Letters}, publisher={Informa UK Limited}, author={Xu, W. Z. and Zhang, Y. F. and Cheng, G. M. and Jian, W. W. and Millett, P. C. and Koch, C. C. and Mathaudhu, S. N. and Zhu, Y. T.}, year={2014}, month={Apr}, pages={176–183} }
 @article{kumar_dasharath_kang_koch_mula_2015, title={Enhancement of mechanical properties of low stacking fault energy brass processed by cryorolling followed by short-annealing}, volume={67}, ISSN={0261-3069}, url={http://dx.doi.org/10.1016/J.MATDES.2014.11.014}, DOI={10.1016/J.MATDES.2014.11.014}, abstractNote={The mechanical properties and microstructural characteristics of ultrafine grained low stacking faulty energy (SFE) brass processed by cryorolling were investigated in the present work. The commercial brass with 18 wt.% Zn was subjected to cryorolling to obtain specimens with different percentage of reduction in area (RA). Short time post-processing annealing was carried out for the specimens with maximum RA (90%) to enhance their ductility. The mechanical properties of all the specimens were assessed by tensile tests and hardness measurements. Microstructural analysis was carried out by optical microscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and electron microscopy (EM). The maximum yield strength (YS) of 600 MPa with 2.1% ductility was obtained for the cryorolled samples with 90% RA. The YS decreased to 452 MPa with a corresponding increase in the ductility (10%) after annealing at 225 °C. The YS of the cryorolled + annealed sample is found to be 465% higher compared to that of the as-received specimens (YS = 80 MPa). Fractography analysis of the 90% rolled specimens showed a brittle fracture; while, presence of dimples marks on the fractured surface of the annealed specimens indicated a ductile failure. The low SFE of the alloy plays a vital role on the deformation mechanisms during cryorolling and simultaneous improvement of the YS and ductility. Hence, improvement in the mechanical properties has been discussed in the light of refinement of microstructure, formation of sub-grains and nano-twins driven by the low SFE.}, journal={Materials & Design}, publisher={Elsevier BV}, author={Kumar, Ravi and Dasharath, S.M. and Kang, P.C. and Koch, Carl C. and Mula, Suhrit}, year={2015}, month={Feb}, pages={637–643} }
 @article{li_saber_xu_zhu_koch_scattergood_2014, title={High-temperature grain size stabilization of nanocrystalline Fe-Cr alloys with Hf additions}, volume={613}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2014.06.099}, abstractNote={The influence of 1–4 at% Hf additions on the thermal stability of mechanically alloyed nanocrystalline Fe–14Cr alloys was studied in this work. XRD-calculated grain size and microhardness results were reported versus isochronal annealing treatments up to 1100 °C. Microstructural evolution was investigated using channeling contrast FIB imaging and TEM. Grain size of samples with 4 at% Hf was found to be maintained in the nanoscale range at temperatures up to 1000 °C. Zener pinning was considered as a major source of high temperature grain size stabilization. By comparing the Orowan strengthening contribution to the total hardness, the deviation of grain size predictions from the actual grain size in Fe–14Cr–4Hf suggests the presence of thermodynamic stabilization by the solute segregation to grain boundaries (GBs). A predictive thermodynamic model indicates that the thermodynamic stabilization can be expected.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Li, Lulu and Saber, Mostafa and Xu, Weizong and Zhu, Yuntian and Koch, Carl C. and Scattergood, Ronald O.}, year={2014}, month={Sep}, pages={289–295} }
 @article{kotan_darling_scattergood_koch_2014, title={Influence of Zr and nano-Y2O3 additions on thermal stability and improved hardness in mechanically alloyed Fe base ferritic alloys}, volume={615}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2014.07.054}, abstractNote={The motivation of this work was driven to improve the thermal stability in systems where polymorphic transformations can result in an additional driving force, upsetting the expected thermodynamic stability. In this study, Fe92Ni8 alloys with Zr and nano-Y2O3 additions were produced by ball milling and then annealed at high temperatures. Emphasis was placed on understanding the effects of dispersed nano-Y2O3 particle additions and their effect on microstructural stability at and above the bcc-to-fcc transformation occurring at 700 °C in Fe–Ni systems. Results reveal that microstructural stability and hardness can be promoted by a combination of Zr and Y2O3 additions, that being mostly effective for stability before and after phase transition, respectively. The mechanical strength of these alloys is achieved by a unique microstructure comprised a ultra-fine grain Fe base matrix, which contains dispersions of both nano-scale in-situ formed Zr base intermetallics and ex-situ added Y2O3 secondary oxide phases. Both of these were found to be essential for a combination of high thermal stability and high mechanical strength properties.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Kotan, Hasan and Darling, Kris A. and Scattergood, Ronald O. and Koch, Carl C.}, year={2014}, month={Dec}, pages={1013–1018} }
 @article{varam_rajulapati_rao_scattergood_murty_koch_2014, title={Loading Rate-Dependent Mechanical Properties of Bulk Two-Phase Nanocrystalline Al-Pb Alloys Studied by Nanoindentation}, volume={45A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-014-2425-8}, number={11}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Varam, Sreedevi and Rajulapati, Koteswararao V. and Rao, K. Bhanu Sankara and Scattergood, Ronald O. and Murty, Korukonda L. and Koch, Carl C.}, year={2014}, month={Oct}, pages={5249–5258} }
 @article{xu_li_saber_koch_zhu_scattergood_2014, title={Nano ZrO2 particles in nanocrystalline Fe-14Cr-1.5Zr alloy powders}, volume={452}, ISSN={["1873-4820"]}, DOI={10.1016/j.jnucmat.2014.05.067}, abstractNote={Here we report on the formation of nano ZrO2 particles in Fe–14Cr–1.5Zr alloy powders synthesized by mechanical alloying. The nano ZrO2 particles were found uniformly dispersed in the ferritic matrix powders with an average size of about 3.7 nm, which rendered the alloy powders so stable that it retained nanocrystalline structure after annealing at 900 °C for 1 h. The ZrO2 nanoparticles have a tetragonal crystal structure and the following orientation relationship with the matrix: (0 0 2)ZrO2//(0 0 2)Matrix and [0 1 0]ZrO2//[1 2 0]Matrix. The size and dispersion of the ZrO2 particles are comparable to those of Y–Ti–O enriched oxides reported in irradiation-resistant ODS alloys. This suggests a potential application of the new alloy powders for nuclear energy applications.}, number={1-3}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Xu, W. Z. and Li, L. L. and Saber, M. and Koch, C. C. and Zhu, Y. T. and Scattergood, R. O.}, year={2014}, month={Sep}, pages={434–439} }
 @article{khoshkhoo_scudino_gemming_thomas_freudenberger_zehetbauer_koch_eckert_2015, title={Nanostructure formation mechanism during in-situ consolidation of copper by room-temperature ball milling}, volume={65}, ISSN={["1873-4197"]}, DOI={10.1016/j.matdes.2014.06.052}, abstractNote={Bulk nanostructured Cu was prepared by in-situ consolidation through room temperature ball milling. The consolidated parts consist of hollow spheres having a diameter which increases with increasing the milling time. Microhardness maps reveal that the distribution of the hardness is relatively homogeneous after 2 h of milling. After 34 h the hardness is higher at the outer edge and decreases toward the inner edge and, finally, after 70 h the distribution is uniform again. Electron microscopic results show that the microstructure after 70 h of milling consists of two types of grains: elongated ultrafine grains with high density of defects and equiaxed nanosized grains produced by dynamic recrystallization. Continuous dynamic recrystallization is the dominant mechanism for the formation of the nanosized grains. Evidence for the occurrence of discontinuous dynamic recrystallization through twinning was also found in a few regions of the in-situ consolidated samples.}, journal={MATERIALS & DESIGN}, author={Khoshkhoo, M. Samadi and Scudino, S. and Gemming, T. and Thomas, J. and Freudenberger, J. and Zehetbauer, M. and Koch, C. C. and Eckert, J.}, year={2015}, month={Jan}, pages={1083–1090} }
 @article{saber_xu_li_zhu_koch_scattergood_2014, title={Size effect of primary Y2O3 additions on the characteristics of the nanostructured ferritic ODS alloys: Comparing as-milled and as-milled/annealed alloys using S/TEM}, volume={452}, ISSN={["1873-4820"]}, DOI={10.1016/j.jnucmat.2014.05.014}, abstractNote={The need for providing S/TEM evidence to clarify the mechanisms of nano-scale precipitate formation was the motivation of this investigation. In this study, an Fe–14Cr–0.4Ti alloy was ball-milled with different amounts of Y2O3 content up to 10 wt.%, and then annealed at temperatures up to 1100 °C. Micron-size Y2O3 particles were substituted for the nano-size counterpart to elucidate the mechanism of oxide precipitate formation. The S/TEM studies revealed that the microstructure of the alloy with 10 wt.% yttria contained amorphous undissolved Y2O3 after ball milling, while a small part of the initial oxide particles were dissolved into the solid solution. Consequently, when the amount of yttria was reduced to 1 wt.%, the amorphous phase of the yttria vanished and the whole content of Y2O3 was dissolved into the BCC solid solution. Defect analysis of precipitates on the annealed samples via S/TEM and micro-hardness studies revealed that the use of micron-size primary oxide particles can produce nano-size precipitates, stable up to temperatures as high as 1100 °C, and uniformly distributed throughout the microstructure. This study indicates that the use of high energy ball milling along with micron-size primary oxide particles can lead to nanostructured ferritic ODS alloys without the use of nano-size primary oxide additions.}, number={1-3}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Saber, Mostafa and Xu, Weizong and Li, Lulu and Zhu, Yuntian and Koch, Carl C. and Scattergood, Ronald O.}, year={2014}, month={Sep}, pages={223–229} }
 @article{mula_setman_youssef_scattergood_koch_2015, title={Structural evolution of Cu(1−X)YX alloys prepared by mechanical alloying: Their thermal stability and mechanical properties}, volume={627}, ISSN={0925-8388}, url={http://dx.doi.org/10.1016/J.JALLCOM.2014.12.114}, DOI={10.1016/J.JALLCOM.2014.12.114}, abstractNote={In the present study, an attempt has been made to synthesize copper based disordered solid solutions by mechanical alloying (MA) of non-equilibrium compositions. The blended compositions of Cu–1% Y, Cu–3% Y, Cu–5% Y and Cu–7.5% Y (at.%) (all the compositions will be addressed as % only hereafter until unless it is mentioned) were ball-milled for 8 h, and then annealed at different temperatures (200–800 °C) for different length of duration (1–5 h) under high purity argon + 2 vol.% H2 atmosphere. X-ray diffraction (XRD) analysis and Gibbs free energy change calculation confirm the formation of disordered solid solution (up to 7.5%) of Y in Cu after milling at a room temperature for 8 h. The XRD grain size was calculated to be as low as 7 nm for 7.5% Y and 22 nm for 1% Y alloy. The grain size was retained within 35 nm even after annealing for 1 h at 800 °C. Transmission electron microscopy (TEM) analysis substantiates the formation of ultra-fine grained nanostructures after milling. Microhardness value of the as-milled samples was quite high (3.0–4.75 GPa) compared to that of pure Cu. The hardness value increased with increasing annealing temperatures up to 400 °C for the alloys containing 3–7.5% Y, and thereafter it showed a decreasing trend. The increase in the hardness after annealing is attributed to the formation of uniformly distributed ultrafine intermetallic phases in the nanocrystalline grains. The stabilization effect is achieved due to segregation of Y to reduce the grain boundary energy to zero and hindrance of dislocation movement due to precipitation of intermetallic phases. The tensile yield strength (σy) of the HPT consolidated nc Cu–1% Y and Cu–3% Y alloys was found to be at least one order of magnitude higher than that of the course grained-Cu counterpart, and the corresponding UTS (σu) value was more than four times higher. The strengthening effect is discussed in the light of the grain size refinement, solid solution strengthening and strain hardening.}, journal={Journal of Alloys and Compounds}, publisher={Elsevier BV}, author={Mula, Suhrit and Setman, Daria and Youssef, Khaled and Scattergood, R.O. and Koch, Carl C}, year={2015}, month={Apr}, pages={108–116} }
 @article{zhang_koch_schwartz_2014, title={Synthesis of Bi2Sr2CaCu2Ox superconductors via direct oxidation of metallic precursors}, volume={27}, ISSN={["1361-6668"]}, DOI={10.1088/0953-2048/27/5/055016}, abstractNote={Bi2Sr2CaCu2Ox(Bi2212)/Ag multifilamentary wires are manufactured via the powder-in-tube process using oxide powders. After deformation, the wires undergo a partial-melt process, resulting in a complex, heterogeneous microstructure containing multiple secondary phases and porosity, limiting the wires’ electrical and mechanical performance. Here, an alternative approach using the direct conversion of metallic precursors (MPs) to Bi2212 is studied. The formation of metallic precursor powders via a mechanical alloy is discussed. The MP powder is then converted to superconducting Bi2212 through a simple two-step heat treatment. By introducing oxygen at a temperature at which Bi2212 is in a stable phase, and holding at an elevated temperature for a sufficient time, the metallic precursors are oxidized and transformed into Bi2212. Several factors that impact the formation and growth of Bi2212 grains are discussed. Peak temperature, holding time and heating rate are shown to affect the MP →Bi2212 conversion, the Bi2201 content and the Bi2212 morphology and density. It is found that Bi2Sr2CuOy (Bi2201) can be the only phase impurity after heat treatment, which is quite different from what is observed in partial-melt processed wires derived from oxide precursors. Lastly, the microstructure at the sample/silver interface suggests larger size and preferred orientation of Bi2212 grains with the aid of a silver surface. Implications for MP Bi2212 wires are discussed.}, number={5}, journal={SUPERCONDUCTOR SCIENCE & TECHNOLOGY}, author={Zhang, Yun and Koch, Carl C. and Schwartz, Justin}, year={2014}, month={May} }
 @article{saber_kotan_koch_scattergood_2013, title={A predictive model for thermodynamic stability of grain size in nanocrystalline ternary alloys}, volume={114}, ISSN={["0021-8979"]}, DOI={10.1063/1.4821040}, abstractNote={This work presents a model for evaluating thermodynamic stabilization of ternary nanocrystalline alloys. It is applicable to alloy systems containing strongly segregating size-misfit solutes with a significant enthalpy of elastic strain and/or immiscible solutes with a positive mixing enthalpy. On the basis of a regular solution model, the chemical and elastic strain energy contributions are incorporated into the mixing enthalpy ΔHmix, and the mixing entropy ΔSmix is obtained using the ideal solution approximation. The Gibbs mixing free energy ΔGmix is minimized with respect to simultaneous variations in grain size and solute segregation parameters. The Lagrange multiplier method is used to obtain numerical solutions for the minimum ΔGmix corresponding to an equilibrium grain size for given alloy compositions. The numerical solutions will serve as a guideline for choosing solutes and assessing the possibility of thermodynamic stabilization. The temperature dependence of the nanocrystalline grain size and interfacial solute excess can be evaluated for selected ternary systems. Model predictions are presented using available input data for a wide range of solvent-solute combinations. The model predictions are compared to experimental results for Cu-Zn-Zr, Fe-Cr-Zr, and Fe-Ni-Zr alloys where thermodynamic stabilization might be effective.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Saber, Mostafa and Kotan, Hasan and Koch, Carl C. and Scattergood, Ronald O.}, year={2013}, month={Sep} }
 @article{chan_lebeau_venkatasubramanian_thomas_stuart_koch_2013, title={Carrier concentration modulation by hot pressing pressure in n-type nanostructured Bi(Se)Te alloy}, volume={103}, ISSN={["1077-3118"]}, DOI={10.1063/1.4823801}, abstractNote={We demonstrate experimentally that an optimal hot pressing pressure is required for high thermoelectric power factor in different n-type Bi(Se)Te alloys for a given processing temperature. This phenomenon is attributed to the variations in carrier concentration, which changes the Seebeck coefficient and therefore the power factor. The variations could arise from the difference in the concentration of charged antisite defects as their formation energy changes with pressures. Furthermore, modifications of the energy gap resulting from the lattice distortions at high pressure also likely play a role.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Chan, Tsung-ta E. and LeBeau, James M. and Venkatasubramanian, Rama and Thomas, Peter and Stuart, Judy and Koch, Carl C.}, year={2013}, month={Sep} }
 @article{mula_panigrahi_kang_koch_2014, title={Effect of microwave sintering over vacuum and conventional sintering of Cu based nanocomposites}, volume={588}, ISSN={0925-8388}, url={http://dx.doi.org/10.1016/J.JALLCOM.2013.11.222}, DOI={10.1016/J.JALLCOM.2013.11.222}, abstractNote={The blend compositions of Cu99Cr1 (All the compositions are in atom% until otherwise mentioned.), Cu94Cr6, Cu99Cr1–4 wt.% SiC (average particle size ∼30 nm) and Cu94Cr6–4 wt.% SiC were ball-milled for 50 h in a stainless steel grinding media. The structural investigation and phase evolution during milling of the same compositions have already been reported in elsewhere ([28]). In the present study, we are reporting effect of microwave sintering on mechanical properties and electrical conductivity over vacuum and conventional sintering carried out at 900 °C. Relative densification and grain coarsening characteristics were investigated and compared. The microstructural features were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The mechanical properties, namely, Vickers hardness and wear resistance, and electrical conductivity were studied to investigate the suitability of the materials for electrical contact applications. The best combination of mechanical properties and electrical conductivity was obtained for microwave sintered specimens. This is possibly due to the enhanced densification and better grain size distribution achieved in microwave sintering technique. Difference in the properties is discussed in the light of electron scattering factor and densification in presence of ultra fine SiC particles in the nanocomposites.}, journal={Journal of Alloys and Compounds}, publisher={Elsevier BV}, author={Mula, Suhrit and Panigrahi, J. and kang, P.C. and Koch, Carl C.}, year={2014}, month={Mar}, pages={710–715} }
 @article{roy_mahesh_atwater_chan_scattergood_koch_2014, title={Grain size stability and hardness in nanocrystalline Cu-Al-Zr and Cu-Al-Y alloys}, volume={598}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2013.11.075}, abstractNote={Cryogenic high energy ball milling has been used to synthesize nanocrystalline Cu–14Al, Cu–12Al–2Zr and Cu–12Al–2Y alloys by mechanical alloying. The alloys were studied with the aim of comparing the effect of substituting Y and Zr in place of Al, in Cu–Al alloys, on the grain size stability at elevated temperatures. The as-milled alloys were subjected to annealing at various temperatures between 200 and 900 °C and the resulting grain morphology has been studied using X-ray diffraction and transmission electron microscopy. The addition of Y results in significantly reduced susceptibility to grain growth whereas in case of CuAl and CuAlZr alloys, the susceptibility to grain growth was much higher. The hardness is substantially increased due to Zr and Y addition in the as-milled CuAl powders. However, the hardness of Cu–12Al–2Zr gradually decreases and approaches that of Cu–14Al alloy after the annealing treatment whereas in case of Cu–12Al–2Y alloy, the relative drop in the hardness is much lower after annealing. Accordingly, the efficacy of grain size stabilization by Y addition at high homologous temperatures has been explained on the basis of a recent thermodynamic stabilization models.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Roy, D. and Mahesh, B. V. and Atwater, M. A. and Chan, T. E. and Scattergood, R. O. and Koch, C. C.}, year={2014}, month={Mar}, pages={217–223} }
 @article{koch_scattergood_saber_kotan_2013, title={High temperature stabilization of nanocrystalline grain size: Thermodynamic versus kinetic strategies}, volume={28}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2012.429}, abstractNote={Abstract}, number={13}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Koch, Carl C. and Scattergood, Ronald O. and Saber, Mostafa and Kotan, Hasan}, year={2013}, month={Jul}, pages={1785–1791} }
 @article{xu_zhang_cheng_jian_millett_koch_mathaudhu_zhu_2013, title={In-situ atomic-scale observation of irradiation-induced void formation}, volume={4}, ISSN={["2041-1723"]}, DOI={10.1038/ncomms3288}, abstractNote={The formation of voids in an irradiated material significantly degrades its physical and mechanical properties. Void nucleation and growth involve discrete atomic-scale processes that, unfortunately, are not yet well understood due to the lack of direct experimental examination. Here we report an in-situ atomic-scale observation of the nucleation and growth of voids in hexagonal close-packed magnesium under electron irradiation. The voids are found to first grow into a plate-like shape, followed by a gradual transition to a nearly equiaxial geometry. Using atomistic simulations, we show that the initial growth in length is controlled by slow nucleation kinetics of vacancy layers on basal facets and anisotropic vacancy diffusivity. The subsequent thickness growth is driven by thermodynamics to reduce surface energy. These experiments represent unprecedented resolution and characterization of void nucleation and growth under irradiation, and might help with understanding the irradiation damage of other hexagonal close-packed materials. The irradiation of crystalline materials is known to create various types of lattice defects, which can degrade mechanical performance. Here, Xu et al. observe the in-situnucleation and growth of atomic-scale voids in magnesium during electron irradiation.}, journal={NATURE COMMUNICATIONS}, author={Xu, Weizong and Zhang, Yongfeng and Cheng, Guangming and Jian, Weiwei and Millett, Paul C. and Koch, Carl C. and Mathaudhu, Suveen N. and Zhu, Yuntian}, year={2013}, month={Aug} }
 @article{zaddach_niu_koch_irving_2013, title={Mechanical Properties and Stacking Fault Energies of NiFeCrCoMn High-Entropy Alloy}, volume={65}, ISSN={1047-4838 1543-1851}, url={http://dx.doi.org/10.1007/S11837-013-0771-4}, DOI={10.1007/s11837-013-0771-4}, number={12}, journal={JOM}, publisher={Springer Science and Business Media LLC}, author={Zaddach, A. J. and Niu, C. and Koch, C. C. and Irving, D. L.}, year={2013}, month={Oct}, pages={1780–1789} }
 @article{khoshkhoo_scudino_bednarcik_kauffmann_bahmanpour_freudenberger_scattergood_zehetbauer_koch_eckert_2014, title={Mechanism of nanostructure formation in ball-milled Cu and Cu–3wt%Zn studied by X-ray diffraction line profile analysis}, volume={588}, ISSN={0925-8388}, url={http://dx.doi.org/10.1016/J.JALLCOM.2013.10.252}, DOI={10.1016/J.JALLCOM.2013.10.252}, abstractNote={The mechanism of nanostructure formation during cryogenic and room-temperature milling of Cu and Cu–3wt%Zn was investigated using X-ray diffraction line profile analysis. For that, the whole powder pattern modeling approach (WPPM) was used to analyze the evolution of microstructural features including coherently scattering domain size, dislocation density, and density of planar faults. It was found that for all sets of experiments, structural decomposition is the dominant mechanism of nanostructure formation during cryomilling. During subsequent RT-milling, grain refinement still occurs by structural decomposition for pure copper. On the other hand, discontinuous dynamic recrystallization is responsible for nanostructure formation during RT-milling of Cu–3wt%Zn. This is attributed to lower stacking-fault energy of Cu–3wt%Zn compared to pure copper. Finally, room temperature milling reveals the occurrence of a detwinning phenomenon.}, journal={Journal of Alloys and Compounds}, publisher={Elsevier BV}, author={Khoshkhoo, M. Samadi and Scudino, S. and Bednarcik, J. and Kauffmann, A. and Bahmanpour, H. and Freudenberger, J. and Scattergood, R. and Zehetbauer, M.J. and Koch, C.C. and Eckert, J.}, year={2014}, month={Mar}, pages={138–143} }
 @article{setman_kerber_bahmanpour_horky_scattergood_koch_zehetbauer_2013, title={Nature and density of lattice defects in ball milled nanostructured copper}, volume={67}, ISSN={["1872-7743"]}, DOI={10.1016/j.mechmat.2013.07.007}, abstractNote={Copper powder of 99.9% purity with particle size in the micrometer range was subjected to high energy ball milling by milling times between 2 and 24 h applying stearic acid as surfactant. The nature and density of lattice defects were determined using differential scanning calorimetry (DSC) and X-ray line profile analysis (XPA). The DSC measurements exhibit a considerable drop of the total stored energy with increasing ball milling time indicating a surprising decrease of lattice defect concentrations by more than one order of magnitude. The results from XPA, however, show that neither the dislocation density, nor the crystallite size can account for this behavior. Rather it is to be attributed to a high concentration of deformation induced vacancy type defects, with their density gradually decreasing during ongoing milling.}, journal={MECHANICS OF MATERIALS}, author={Setman, D. and Kerber, M. and Bahmanpour, H. and Horky, J. and Scattergood, R. O. and Koch, C. C. and Zehetbauer, M. J.}, year={2013}, month={Dec}, pages={59–64} }
 @article{jian_cheng_xu_koch_wang_zhu_mathaudhu_2013, title={Physics and model of strengthening by parallel stacking faults}, volume={103}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4822323}, DOI={10.1063/1.4822323}, abstractNote={We have recently reported that parallel stacking faults (SFs) can tremendously increase the strength of a magnesium alloy. The strengthening is found to increase linearly with the reciprocal of the mean SF spacing, d. In this study we analyze dislocation interactions with SFs, and then propose a physics-based model to explain the observed relationship between yield strength and SFs spacing. Similar to the empirical Hall-Petch relationship for grain size, it is expected that this strengthening mechanism will hold true for a variety of materials engineered with parallel spaced stacking faults over a wide range of fault spacing.}, number={13}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Jian, W. W. and Cheng, G. M. and Xu, W. Z. and Koch, C. C. and Wang, Q. D. and Zhu, Y. T. and Mathaudhu, S. N.}, year={2013}, month={Sep}, pages={133108} }
 @article{mahesh_singh raman_scattergood_koch_2013, title={RETRACTED: Fe–Cr–Ni–Zr alloys with bi-modal grain size distribution: Synthesis, mechanical properties and oxidation resistance}, volume={574}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/J.MSEA.2013.02.049}, DOI={10.1016/J.MSEA.2013.02.049}, abstractNote={This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor. The article contains similar content to a paper of the authors that had already appeared in J MATER SCI, 47(2012) 7735–7743. http://dx.doi.org/10.1007/s10853-012-6686-6. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data, including any author's own data, should be appropriately cited. As such this article represents an abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Mahesh, B.V. and Singh Raman, R.K. and Scattergood, R.O. and Koch, C.C.}, year={2013}, month={Jul}, pages={235–242} }
 @article{tao_zhu_scattergood_koch_2013, title={The thermal stability of high-energy ball-milled nanostructured Cu}, volume={50}, ISSN={0261-3069}, url={http://dx.doi.org/10.1016/J.MATDES.2013.02.083}, DOI={10.1016/J.MATDES.2013.02.083}, abstractNote={The thermal stability of nanostructured (NS) Cu prepared by high-energy ball milling was investigated. The as-prepared samples were isothermal annealed for 1 h in the temperature range of 200–1000 °C. Effects of annealing on NS Cu samples were studied by means of Vickers hardness test, differential scanning calorimetry (DSC) and stress relaxation test. The exceptional high microhardness of as-prepared Cu sample of 1.7 GPa was not detected to decrease after annealing at 500 °C for 1 h with corresponding small value of activation volumes V* of 22.6b3 and high value of strain rate sensitivity m of 0.0176. A prominent decrease of microhardness was detected after higher temperature annealing with a rapidly increase of activation volume and decrease of strain rate sensitivity. The present investigation demonstrates that the thermal stability of NS Cu prepared by high-energy ball milling is determined by not only the grain size but also the microstructure of grain boundaries, and during annealing process, the strain release process occurred prior to the grain growth process, therefore, the NS Cu has a relatively high thermal stability.}, journal={Materials & Design}, publisher={Elsevier BV}, author={Tao, J.M. and Zhu, X.K. and Scattergood, R.O. and Koch, C.C.}, year={2013}, month={Sep}, pages={22–26} }
 @article{atwater_mula_scattergood_koch_2013, title={Thermal Stability of Nanocrystalline Copper Alloyed with Antimony}, volume={44A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-013-1891-8}, number={12}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Atwater, Mark A. and Mula, Suhrit and Scattergood, Ronald O. and Koch, Carl C.}, year={2013}, month={Dec}, pages={5611–5616} }
 @article{kotan_darling_saber_scattergood_koch_2013, title={Thermal stability and mechanical properties of nanocrystalline Fe-Ni-Zr alloys prepared by mechanical alloying}, volume={48}, ISSN={["0022-2461"]}, DOI={10.1007/s10853-013-7652-7}, number={24}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Kotan, Hasan and Darling, Kris A. and Saber, Mostafa and Scattergood, Ronald O. and Koch, Carl C.}, year={2013}, month={Dec}, pages={8402–8411} }
 @article{darling_kecskes_atwater_semones_scattergood_koch_2013, title={Thermal stability of nanocrystalline nickel with yttrium additions}, volume={28}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2013.9}, number={13}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Darling, K. A. and Kecskes, L. J. and Atwater, M. and Semones, J. and Scattergood, R. O. and Koch, C. C.}, year={2013}, month={Jul}, pages={1813–1819} }
 @article{saber_kotan_koch_scattergood_2013, title={Thermodynamic stabilization of nanocrystalline binary alloys}, volume={113}, ISSN={["0021-8979"]}, DOI={10.1063/1.4791704}, abstractNote={The work presented here was motivated by the need to develop a predictive model for thermodynamic stabilization of binary alloys that is applicable to strongly segregating size-misfit solutes, and that can use available input data for a wide range of solvent-solute combinations. This will serve as a benchmark for selecting solutes and assessing the possible contribution of thermodynamic stabilization for development of high-temperature nanocrystalline alloys. Following a regular solution model that distinguishes the grain boundary and grain interior volume fractions by a transitional interface in a closed system, we include both the chemical and elastic strain energy contributions to the mixing enthalpy ΔHmix using an appropriately scaled linear superposition. The total Gibbs mixing free energy ΔGmix is minimized with respect to simultaneous variations in the grain-boundary volume fraction and the solute contents in the grain boundary and grain interior. The Lagrange multiplier method was used to obtain numerical solutions with the constraint of fixed total solute content. The model predictions are presented using a parametric variation of the required input parameters. Applications are then given for the dependence of the nanocrystalline grain size on temperature and total solute content for selected binary systems where experimental results suggest that thermodynamic stabilization could be effective.}, number={6}, journal={JOURNAL OF APPLIED PHYSICS}, author={Saber, Mostafa and Kotan, Hasan and Koch, Carl C. and Scattergood, Ronald O.}, year={2013}, month={Feb} }
 @article{jian_cheng_xu_yuan_tsai_wang_koch_zhu_mathaudhu_2013, title={Ultrastrong Mg Alloy via Nano-spaced Stacking Faults}, volume={1}, ISSN={2166-3831}, url={http://dx.doi.org/10.1080/21663831.2013.765927}, DOI={10.1080/21663831.2013.765927}, abstractNote={Mg alloys are among the lightest alloys but they are usually weak. Here we report a new mechanism to make them ultrastrong while maintaining good ductility. Stacking faults with nanoscale spacing were introduced into a Mg–8.5Gd–2.3Y–1.8Ag–0.4Zr (wt%) alloy by conventional hot rolling, which produced a yield strength of ∼575 MPa, an ultimate strength of ∼600 MPa, and a uniform elongation of ∼5.2 %. Low stacking fault (SF) energy enabled the introduction of a high density of SFs, which impeded dislocation slip and promoted dislocation accumulation. These findings provide guidance for developing Mg alloys with superior mechanical properties.}, number={2}, journal={Materials Research Letters}, publisher={Informa UK Limited}, author={Jian, W. W. and Cheng, G. M. and Xu, W. Z. and Yuan, H. and Tsai, M. H. and Wang, Q. D. and Koch, C. C. and Zhu, Y. T. and Mathaudhu, S. N.}, year={2013}, month={Mar}, pages={61–66} }
 @article{kotan_darling_saber_scattergood_koch_2013, title={An in situ experimental study of grain growth in a nanocrystalline Fe91Ni8Zr1 alloy}, volume={48}, ISSN={["0022-2461"]}, DOI={10.1007/s10853-012-7002-1}, abstractNote={Grain growth and microstructural evolution of thermally stabilized Fe91Ni8Zr1 were investigated by in situ and ex situ studies. Our investigations suggest that the microstructural evolution is fairly slow and the microstructure shows stabilization up to about 700 °C. Above this temperature, a certain fraction of grains grow abnormally into the nanocrystalline matrix, resulting in a bimodal microstructure and causing the complete loss of thermal stability. The reason for abnormal grain growth and the loss of thermal stability is identified as the appearance of the fcc γ-phase and consequent reduction in the total area of grain boundaries and the overall stored energy.}, number={5}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Kotan, Hasan and Darling, Kris A. and Saber, Mostafa and Scattergood, Ronald O. and Koch, Carl C.}, year={2013}, month={Mar}, pages={2251–2257} }
 @article{mahesh_raman_koch_2012, title={Bimodal grain size distribution: an effective approach for improving the mechanical and corrosion properties of Fe–Cr–Ni alloys}, volume={47}, ISSN={0022-2461 1573-4803}, url={http://dx.doi.org/10.1007/S10853-012-6686-6}, DOI={10.1007/S10853-012-6686-6}, number={22}, journal={Journal of Materials Science}, publisher={Springer Science and Business Media LLC}, author={Mahesh, B. V. and Raman, R. K. Singh and Koch, C. C.}, year={2012}, month={Jul}, pages={7735–7743} }
 @article{bahmanpour_youssef_horky_setman_atwater_zehetbauer_scattergood_koch_2012, title={Deformation twins and related softening behavior in nanocrystalline Cu-30% Zn alloy}, volume={60}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2012.02.036}, abstractNote={Nanocrystalline Cu–30% Zn samples were produced by high energy ball milling at 77 K and room temperature. Cryomilled flakes were further processed by ultrahigh strain high pressure torsion (HPT) or room temperature milling to produce bulk artifact-free samples. Deformation-induced grain growth and a reduction in twin probability were observed in HPT consolidated samples. Investigations of the mechanical properties by hardness measurements and tensile tests revealed that at small grain sizes of less than ∼35 nm Cu–30% Zn deviates from the classical Hall–Petch relation and the strength of nanocrsytalline Cu–30% Zn is comparable with that of nanocrystalline pure copper. High resolution transmission electron microscopy studies show a high density of finely spaced deformation nanotwins, formed due to the low stacking fault energy of 14 mJ m–2 and low temperature severe plastic deformation. Possible softening mechanisms proposed in the literature for nanotwin copper are addressed and the twin-related softening behavior in nanotwinned Cu is extended to the Cu–30% Zn alloy based on detwinning mechanisms.}, number={8}, journal={ACTA MATERIALIA}, author={Bahmanpour, Hamed and Youssef, Khaled M. and Horky, Jelena and Setman, Daria and Atwater, Mark A. and Zehetbauer, Michael J. and Scattergood, Ronald O. and Koch, Carl C.}, year={2012}, month={May}, pages={3340–3349} }
 @article{kotan_saber_koch_scattergood_2012, title={Effect of annealing on microstructure, grain growth, and hardness of nanocrystalline Fe–Ni alloys prepared by mechanical alloying}, volume={552}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2012.05.045}, DOI={10.1016/j.msea.2012.05.045}, abstractNote={Fe–xNi alloys from x = 0 to x = 15 with an as-milled grain size and hardness in the range of 8–11 nm and 8.5–9.5 GPa, respectively, were synthesized by ball milling. Microstructural changes, hardness, and grain growth due to annealing were characterized using X-ray diffractometry, microhardness, focused ion beam channeling contrast imaging, and optical microscopy. It was found that the composition range of single bcc phase was extended by ball milling. Subsequent annealing of MA samples resulted in reduction of hardness and extensive grain growth. It indicates that nickel has no significant effect on thermal stabilization of iron. Retained austenite was observed for Fe–8Ni and Fe–10Ni alloys annealed in the two-phase region and effect of as-milled structure on retained austenite formation was discussed.}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Kotan, H. and Saber, M. and Koch, C.C. and Scattergood, R.O.}, year={2012}, month={Aug}, pages={310–315} }
 @article{kotan_darling_saber_koch_scattergood_2013, title={Effect of zirconium on grain growth and mechanical properties of a ball-milled nanocrystalline FeNi alloy}, volume={551}, ISSN={0925-8388}, url={http://dx.doi.org/10.1016/j.jallcom.2012.10.179}, DOI={10.1016/j.jallcom.2012.10.179}, abstractNote={Grain growth of ball-milled pure Fe, Fe92Ni8, and Fe91Ni8Zr1 alloys has been studied using X-ray diffractometry (XRD), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). Mechanical properties with respect to compositional changes and annealing temperatures have been investigated using microhardness and shear punch tests. We found the rate of grain growth of the Fe91Ni8Zr1 alloy to be much less than that of pure Fe and the Fe92Ni8 alloy at elevated temperatures. The microstructure of the ternary Fe91Ni8Zr1 alloy remains nanoscale up to 700 °C where only a few grains grow abnormally whereas annealing of pure iron and the Fe92Ni8 alloy leads to extensive grain growth. The grain growth of the ternary alloy at high annealing temperatures is coupled with precipitation of Fe2Zr. A fine dispersion of precipitated second phase is found to promote the microstructural stability at high annealing temperatures and to increase the hardness and ultimate shear strength of ternary Fe91Ni8Zr1 alloy drastically when the grain size is above nanoscale.}, journal={Journal of Alloys and Compounds}, publisher={Elsevier BV}, author={Kotan, Hasan and Darling, Kris A. and Saber, Mostafa and Koch, Carl C. and Scattergood, Ronald O.}, year={2013}, month={Feb}, pages={621–629} }
 @article{gupta_raman_koch_2012, title={Electrochemical characteristics of nano and microcrystalline Fe-Cr alloys}, volume={47}, ISSN={["1573-4803"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84864455905&partnerID=MN8TOARS}, DOI={10.1007/s10853-012-6529-5}, number={16}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Gupta, Rajeev K. and Raman, R. K. Singh and Koch, C. C.}, year={2012}, month={Aug}, pages={6118–6124} }
 @article{roy_mitra_ojo_singh_kolesnikov_lojkowski_scattergood_koch_manna_2012, title={Evaluation of mechanical properties of partially amorphous and nanocrystalline Al50Ti40Si10 composites prepared by mechanical alloying and hot isostatic pressing}, volume={555}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2012.06.028}, abstractNote={Mechanically alloyed in situ nano Al3Ti dispersed Al50Ti40Si10 amorphous matrix alloy powder was consolidated by hot isostatic pressing in the temperature range of 300–600 °C with a pressure of 1.2 GPa and holed at this temperature for 10 min. Microstructural and phase evolution studies of the mechanically alloyed powder and sintered compacts were conducted by X-ray diffraction and transmission electron microscopy. Alloy sintered at 500 °C recorded an excellent combination of high hardness (8.61 GPa), compressive strength (1212 MPa) and Young's modulus (149 GPa). Furthermore, these results have been compared with that of earlier studies based on conventional sintering (CCS), and high pressure sintering (HPS).}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Roy, D. and Mitra, R. and Ojo, O. A. and Singh, S. S. and Kolesnikov, D. and Lojkowski, W. and Scattergood, R. O. and Koch, C. C. and Manna, I.}, year={2012}, month={Oct}, pages={21–27} }
 @article{roy_atwater_youssef_ledford_scattergood_koch_2013, title={Studies on thermal stability, mechanical and electrical properties of nano crystalline Cu99.5Zr0.5 alloy}, volume={558}, ISSN={["0925-8388"]}, DOI={10.1016/j.jallcom.2012.11.004}, abstractNote={Cryogenic high energy ball milling was used to synthesize nanocrystalline Cu and Cu99.5Zr0.5 alloys by mechanical alloying and consolidation by hot pressing at 550 °C temperature. The grain size stability of nanocrystalline Cu is improved by the Zr addition. Microstructural characterization using X-ray diffraction and transmission electron microscopy provided evidence for the formation of a Cu–Zr alloy solid solution with nanocrystalline size after hot pressing. The alloy exhibited a higher hardness (3.31 GPa), and shear strength (550 MPa) than nano-crystalline pure Cu however, the electrical resistivity is increased in the alloy.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Roy, Debdas and Atwater, Mark A. and Youssef, Khaled and Ledford, John Christopher and Scattergood, Ronald O. and Koch, Carl C.}, year={2013}, month={May}, pages={44–49} }
 @article{atwater_scattergood_koch_2013, title={The stabilization of nanocrystalline copper by zirconium}, volume={559}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2012.08.092}, abstractNote={Alloys of copper (Cu) and zirconium (Zr) were generated by mechanical alloying via cryogenic, high-energy ball milling and then annealed to a maximum temperature of 1000 °C. The addition of only 1 at% Zr to Cu was found effective at stabilizing the grains in the nanocrystalline state to homologous temperatures in excess of 0.85. When Zr was added in concentrations of 2 and 5 at%, the alloys underwent substantial hardening during annealing, but grain size stability was not enhanced. The mechanism of grain size stabilization was investigated using thermodynamic and kinetic modeling. Zr is predicted to significantly reduce the grain boundary energy of Cu via segregation, but simplifications in the thermodynamic model do not capture high temperature behavior. Kinetically, good correlation between calculation and experimental observation was found by applying estimations for the limiting grain size and Orowan strengthening via second-phase pinning. Both thermodynamic and kinetic mechanisms may be active during annealing, but kinetic parameters appear to be sufficient in explaining the excellent stability of nanocrystalline Cu, even at low Zr concentration.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Atwater, Mark A. and Scattergood, Ronald O. and Koch, Carl C.}, year={2013}, month={Jan}, pages={250–256} }
 @article{atwater_bahmanpour_scattergood_koch_2013, title={The thermal stability of nanocrystalline cartridge brass and the effect of zirconium additions}, volume={48}, ISSN={["0022-2461"]}, DOI={10.1007/s10853-012-6731-5}, number={1}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Atwater, Mark A. and Bahmanpour, Hamed and Scattergood, Ronald O. and Koch, Carl C.}, year={2013}, month={Jan}, pages={220–226} }
 @article{atwater_roy_darling_butler_scattergood_koch_2012, title={The thermal stability of nanocrystalline copper cryogenically milled with tungsten}, volume={558}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2012.07.117}, abstractNote={Copper (Cu) was cryogenically milled with tungsten (W) in a high-energy ball mill. The process created W particles dispersed in a nanocrystalline Cu matrix. These "alloys" were then annealed to a maximum temperature of 800 °C. The addition of W stabilized the Cu at∼40 nm during annealing to 400 °C for a 1 at% W composition and to 600 °C for 10 at% W. As evidenced through hardness measurement, the W provided a significant increase in strength over pure Cu, and the 10 at% W material maintained a 2.6 GPa hardness after annealing at 800 °C. The stabilization and strengthening mechanisms are compared against theoretical prediction and found to be in good agreement. Although the strength and stability are significantly improved over pure Cu, the maximum benefit was hindered by an extremely broad W particle size distribution (∼5–5000 nm). For the 10 at% W alloy, only half of the added W was reduced to nanoscale where kinetic pinning and strengthening become most effective.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Atwater, Mark A. and Roy, Debdas and Darling, Kristopher A. and Butler, Brady G. and Scattergood, Ronald O. and Koch, Carl C.}, year={2012}, month={Dec}, pages={226–233} }
 @article{saber_kotan_koch_scattergood_2012, title={Thermal stability of nanocrystalline Fe-Cr alloys with Zr additions}, volume={556}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2012.07.045}, abstractNote={The primary objective of this work was to determine the influence of 1–4 at% Zr additions on the thermal stability of mechanically alloyed nanocrystalline Fe–Cr alloys containing 10 and 18 at% Cr. Grain sizes based on XRD, along with microhardness changes, are reported for isochronal annealing treatments up to 1000 °C. Microstructure investigations were done using optical microscopy, channeling contrast FIB imaging, and TEM. Grain size stabilization in the nanaoscale range was maintained up to 900 °C by adding 2 at% Zr. Kinetic pinning by nanoscale intermetallic particles was identified as one source of high temperature grain size stabilization. Intermetallic particles also contribute to strengthening in addition to the Hall–Petch effect. The analysis of microhardness, XRD data, and measured values from the TEM image for Fe-10 at% Cr with 2 at% Zr suggested that both thermodynamic and kinetic mechanisms would contribute to grain size stabilization. There was no significant difference in the results for the 10 and 18 at% Cr alloys, which indicates that the α→γ transformation does not influence the grain size stabilization.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Saber, Mostafa and Kotan, Hasan and Koch, Carl C. and Scattergood, Ronald O.}, year={2012}, month={Oct}, pages={664–670} }
 @article{mula_bahmanpour_mal_kang_atwater_jian_scattergood_koch_2012, title={Thermodynamic feasibility of solid solubility extension of Nb in Cu and their thermal stability}, volume={539}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2012.01.104}, DOI={10.1016/j.msea.2012.01.104}, abstractNote={A series of Cu–xNb (x = 1–15 at.%2) alloys have been investigated to study the metastable solid solubility extension of Nb in Cu by mechanical alloying. Analysis of X-ray diffraction and Gibbs free energy change confirmed that 7.5% of Nb was metastably dissolved in Cu after 8 h of milling at room temperature although Cu–Nb is a system with positive heat of mixing. The solid solubility could be extended up to 10% after enhancing milling duration to 16 h. Detailed thermodynamic analysis revealed that the additional energy stored during mechanical alloying could overcome the required energy barrier as per Miedema's model for the formation of disordered solid solution. The extended solid solubility has been explained along with the other possible mechanisms. Extensive annealing experiments and structural investigation revealed that the supersaturated solid solution is completely stable up to 400 °C. The matrix grains were stabilized and retained their size, ∼25 nm, even after annealing at 600 °C. Microhardness measurement and grain size analysis show that the dissolution of Nb in Cu has a larger strengthening effect than that of free Nb in the compositions.}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Mula, Suhrit and Bahmanpour, H. and Mal, S. and Kang, P.C. and Atwater, M. and Jian, W. and Scattergood, R.O. and Koch, Carl C.}, year={2012}, month={Mar}, pages={330–336} }
 @article{mula_pabi_koch_padhi_ghosh_2012, title={Workability and mechanical properties of ultrasonically cast Al–Al2O3 nanocomposites}, volume={558}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2012.08.032}, DOI={10.1016/j.msea.2012.08.032}, abstractNote={Workability and mechanical properties of the ultrasonically cast Al–X wt% Al2O3 (X=2, 3.57 and 4.69) metal matrix nanocomposites were reported in the present investigation. The Al–Al2O3 (average size ∼10 nm) composites showed maximum reduction ratios of 2, 1.75 and 1.41 at room temperature, and 8, 7 and 6 at 300 °C. The elastic modulus, nanoindentation hardness, microhardness and Vickers hardness were measured on the as-cast, cold and hot rolled specimens. The tensile properties were also evaluated for the as-cast composites for different wt% of reinforcement. The microstructural examination was done by optical, scanning and transmission electron microscopy. The strength and workability of the nanocomposites were discussed in the light of dislocation/particle interaction, particle size and its concentration, inter-particle spacing and working temperature. 2 wt% of Al2O3 reinforcement showed better combination of workability and mechanical properties possibly due to better distribution of particulates in the matrix.}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Mula, Suhrit and Pabi, S.K. and Koch, Carl C and Padhi, P. and Ghosh, S.}, year={2012}, month={Dec}, pages={485–491} }
 @article{bahmanpour_kauffmann_khoshkhoo_youssef_mula_freudenberger_eckert_scattergood_koch_2011, title={Effect of stacking fault energy on deformation behavior of cryo-rolled copper and copper alloys}, volume={529}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2011.09.022}, abstractNote={Abstract Pure copper and Cu–12.1 at.%Al–4.1 at.%Zn alloy were subjected to rolling in liquid nitrogen. TEM studies showed that dynamic recovery during the deformation process was effectively suppressed and hence microstructures with dislocation substructure and deformation twins were formed. Mechanical properties were assessed via microtensile testing that shows improved yield strength, 520 ± 20 MPa, and ductility, 22%, in the case of pure copper. Alloying with Al and Zn results in reduction in stacking fault energy (SFE) which can contribute to enhanced strength and good ductility. Physical activation volume obtained via stress relaxation tests is 26 b 3 , and 8 b 3 for pure copper, and Cu–12.1 at.%Al–4.1 at.%Zn, respectively. The effect of SFE on work hardening rate of samples is discussed. Although twinning is observed in the alloy, it is concluded that network dislocation strengthening plays the major role in determining the mechanical properties.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Bahmanpour, H. and Kauffmann, A. and Khoshkhoo, M. S. and Youssef, K. M. and Mula, S. and Freudenberger, J. and Eckert, J. and Scattergood, R. O. and Koch, C. C.}, year={2011}, month={Nov}, pages={230–236} }
 @article{youssef_sakaliyska_bahmanpour_scattergood_koch_2011, title={Effect of stacking fault energy on mechanical behavior of bulk nanocrystalline Cu and Cu alloys}, volume={59}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2011.05.052}, abstractNote={Twinning and dislocation slip are two major and competing modes of plastic deformation in metals and alloys. In addition to controlling the dislocation substructure in coarse grained materials, stacking fault energy (SFE) also affects the propensity to form deformation twins. However, the influence of SFE has not been fully explored in nanocrystalline materials. Here the role of SFE in deformation twinning and work hardening was systematically studied in bulk artifact-free, nanocrystalline (nc) Cu (SFE 55 mJ m−2), and a nc Cu–12.1 at.% Al–4.1 at.% Zn alloy (SFE 7 mJ m−2). The nc Cu (23 nm) and nc Cu alloy (22 nm) were synthesized using in situ consolidation during cryo and room temperature milling. Both materials showed ultra-high tensile strength, significant strain hardening, and good ductility. The nc Cu alloy exhibits a higher yield strength and lower uniform elongation (1067 ± 20 MPa, 6.5%) than that of nc Cu (790 ± 12 MPa, 14%). The SFE variation played a significant role in strengthening the nc Cu alloy. High resolution transmission electron microscopy analyses revealed that the low SFE of the nc Cu alloy alters the deformation mechanism from a dislocation-controlled deformation, which allows for the higher strain hardening observed in the nc Cu, to a twin-controlled deformation.}, number={14}, journal={ACTA MATERIALIA}, author={Youssef, Khaled and Sakaliyska, Miroslava and Bahmanpour, Hamed and Scattergood, Ronald and Koch, Carl}, year={2011}, month={Aug}, pages={5758–5764} }
 @article{youssef_wang_liao_mathaudhu_kecskes_zhu_koch_2011, title={High hardness in a nanocrystalline Mg97Y2Zn1 alloy}, volume={528}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2011.06.017}, abstractNote={A nanocrystalline Mg97Y2Zn1 alloy was prepared with an average grain size of 21 nm by mechanical alloying of elemental powders. The structure of the alloy was characterized by X-ray diffraction and transmission electron microscopy. The hardness of the alloy as-milled for 8 h at room temperature was 2.1 GPa. After compaction and annealing at 573 K, the average grain size slightly increases to 28 nm with an increase in hardness to 2.4 GPa. These are the highest values for hardness yet reported for a crystalline Mg-based (>95% Mg) alloy. Possible factors leading to this high strength are discussed.}, number={25-26}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Youssef, K. M. and Wang, Y. B. and Liao, X. Z. and Mathaudhu, S. N. and Kecskes, L. J. and Zhu, Y. T. and Koch, C. C.}, year={2011}, month={Sep}, pages={7494–7499} }
 @article{bahmanpour_youssef_scattergood_koch_2011, title={Mechanical behavior of bulk nanocrystalline copper alloys produced by high energy ball milling}, volume={46}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-011-5312-3}, number={19}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Bahmanpour, H. and Youssef, K. M. and Scattergood, R. O. and Koch, C. C.}, year={2011}, month={Oct}, pages={6316–6322} }
 @article{mula_sahani_pratihar_mal_koch_2011, title={Mechanical properties and electrical conductivity of Cu–Cr and Cu–Cr–4% SiC nanocomposites for thermo-electric applications}, volume={528}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2011.03.040}, DOI={10.1016/j.msea.2011.03.040}, abstractNote={The present work investigates the feasibility of microwave sintering to produce bulk metal-based nanocomposites having blend composition of Cu99Cr1, Cu94Cr6, Cu99Cr1–4 wt.% SiC and Cu94Cr6–4 wt.% SiC (average particle size ∼30 nm). The 50 h ball-milled samples were uniaxially pressed, and then pellets were sintered at 800 °C, 900 °C and 1000 °C for a constant soaking period of 30 min by microwave sintering technique. Microstructural characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Sintered compacts resulted a highly densified compacts (∼95% relative density) while retaining ultra-fine grains (100–200 nm) in the matrix. The mechanical properties, namely, hardness and wear resistance, and electrical conductivity of the sintered specimens were also evaluated. The best combination of mechanical properties (e.g. hardness ∼2.4 GPa) and electrical conductivity (60.3% of IACS) were obtained for Cu94Cr6–4 wt.% SiC sintered at 900 °C. This is possibly due to presence of ultra-fine grains in the bulk samples, good densification and proper bonding between particles. The results were analyzed in the light of interactions of microwaves between metallic matrix and microwave susceptive SiC particulates.}, number={13-14}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Mula, Suhrit and Sahani, Pankajini and Pratihar, S.K. and Mal, Siddhartha and Koch, Carl C.}, year={2011}, month={May}, pages={4348–4356} }
 @article{kang_chen_zhang_wu_mula_koch_2011, title={Oxidation protection of carbon fibers by a reaction sintered nanostructured SiC coating}, volume={206}, ISSN={0257-8972}, url={http://dx.doi.org/10.1016/j.surfcoat.2011.07.016}, DOI={10.1016/j.surfcoat.2011.07.016}, abstractNote={A nanostructured SiC coating was prepared on the surface of carbon fibers by slurry coating and in situ reaction sintering. Phases of the coating were identified by X-ray diffraction, and features and structure were investigated by scanning electron microscopy and transmission electron microscopy. The oxidation resistant properties of the carbon fibers with and without the SiC coating were studied using isothermal oxidation. The results show that the nanostructured SiC coating was uniform and its coverage was complete. The oxidation activation energy of the fibers increased about 25% and the oxidation resistant of the coated fibers increases significantly.}, number={2-3}, journal={Surface and Coatings Technology}, publisher={Elsevier BV}, author={Kang, P.C. and Chen, G.Q. and Zhang, B. and Wu, G.H. and Mula, S. and Koch, C.C.}, year={2011}, month={Oct}, pages={305–311} }
 @article{kauffmann_freudenberger_geissler_yin_schillinger_sarma_bahmanpour_scattergood_khoshkhoo_wendrock_et al._2011, title={Severe deformation twinning in pure copper by cryogenic wire drawing}, volume={59}, ISSN={1359-6454}, url={http://dx.doi.org/10.1016/j.actamat.2011.08.042}, DOI={10.1016/j.actamat.2011.08.042}, abstractNote={The effect of low-temperature on the active deformation mechanism is studied in pure copper. For this purpose, cryogenic wire drawing at liquid nitrogen temperature (77 K) was performed using molybdenum disulfide lubrication. Microstructural investigation and texture analysis revealed severe twin formation in the cryogenically drawn copper, with a broad twin size distribution. The spacing of the observed deformation twins ranges from below 100 nm, as reported in previous investigations, up to several micrometers. The extent of twin formation, which is significantly higher when compared to other cryo-deformation techniques, is discussed with respect to the state of stress and the texture evolution during wire drawing.}, number={20}, journal={Acta Materialia}, publisher={Elsevier BV}, author={Kauffmann, A. and Freudenberger, J. and Geissler, D. and Yin, S. and Schillinger, W. and Sarma, V. Subramanya and Bahmanpour, H. and Scattergood, R. and Khoshkhoo, M.S. and Wendrock, H. and et al.}, year={2011}, month={Dec}, pages={7816–7823} }
 @article{darling_vanleeuwen_semones_koch_scattergood_kecskes_mathaudhu_2011, title={Stabilized nanocrystalline iron-based alloys: Guiding efforts in alloy selection}, volume={528}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2011.02.080}, DOI={10.1016/j.msea.2011.02.080}, abstractNote={Using a modified regular solution model for grain boundary solute segregation, the relative thermal stability of a number of Fe-based nanocrystalline binary alloys was predicted with considerable accuracy. It was found that nanocrystalline iron was strongly stabilized by zirconium, moderately stabilized by tantalum, and not significantly stabilized by nickel or chromium. These findings are fully in line with the aforementioned predictions. This success with iron based alloys highlights the utility of this practical approach to selecting stabilizing solutes for nanocrystalline alloys.}, number={13-14}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Darling, K.A. and VanLeeuwen, B.K. and Semones, J.E. and Koch, C.C. and Scattergood, R.O. and Kecskes, L.J. and Mathaudhu, S.N.}, year={2011}, month={May}, pages={4365–4371} }
 @article{sahani_mula_roy_kang_koch_2011, title={Structural investigation of vacuum sintered Cu-Cr and Cu-Cr-4% SIC nanocomposites prepared by mechanical alloying}, volume={528}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2011.06.086}, abstractNote={Abstract Attempts have been made to synthesize Cu 99 Cr 1 , Cu 94 Cr 6 , Cu 99 Cr 1 –4% SiC and Cu 94 Cr 6 –4% SiC (∼30 nm) nanocomposites for thermo-electric applications. The blend compositions were ball-milled for 50 h in a stainless steel grinding media. The microstructural features were characterized by X-ray diffraction (XRD), Nano zeta sizer, Fourier transforms infrared radiation, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Analysis of crystallite size, lattice microstrain and lattice parameter of Cu revealed that the dissolution of Cr increased up to 1 at.% in presence of nanosize SiC particles during milling. The compact specimens were subjected to vacuum sintering (900 °C and 1000 °C for 1 h), and the results were compared with that of microwave sintered samples. The mechanical properties like Vickers hardness and electrical conductivity of the sintered specimens were also investigated.}, number={25-26}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Sahani, P. and Mula, Suhrit and Roy, P. K. and Kang, P. C. and Koch, C. C.}, year={2011}, month={Sep}, pages={7781–7789} }
 @article{gupta_darling_singh raman_ravi_koch_murty_scattergood_2012, title={Synthesis, characterization and mechanical behaviour of an in situ consolidated nanocrystalline FeCrNi alloy}, volume={47}, ISSN={0022-2461 1573-4803}, url={http://dx.doi.org/10.1007/S10853-011-5986-6}, DOI={10.1007/S10853-011-5986-6}, number={3}, journal={Journal of Materials Science}, publisher={Springer Science and Business Media LLC}, author={Gupta, Rajeev K. and Darling, Kris S. and Singh Raman, R. K. and Ravi, K. R. and Koch, Carl C. and Murty, B. S. and Scattergood, R. O.}, year={2012}, month={Feb}, pages={1562–1566} }
 @article{gobien_murty_scattergood_goodwin_koch_2010, title={Creep behavior of ultra-fine grained Zn-4.5Al}, volume={527}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2010.08.020}, abstractNote={Creep tests were performed at 295 and 373 K on a cryogenically ball-milled Zn–4.5Al alloy. Creep tests on the as-milled microstructure having an average grain size of 260 nm showed clear signs of a threshold stress. The same material after a targeted heat treatment showed no signs of a threshold stress for the same alloy with an average grain size of 510 nm. In both cases stress exponent (n) values close to 1 and activation energies close to that of grain boundary diffusion were noted. Potential causes of the threshold stress are proposed as being a nanocrystalline oxide dispersion or non-uniform solute segregation, each of which could potentially interfere with grain boundary vacancy transfer mechanisms.}, number={27-28}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Gobien, J. M. and Murty, K. L. and Scattergood, R. O. and Goodwin, F. and Koch, C. C.}, year={2010}, month={Oct}, pages={7382–7386} }
 @article{gollapudi_rajulapati_charit_koch_scattergood_murty_2010, title={Creep in nanocrystalline materials: Role of stress assisted grain growth}, volume={527}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2010.05.048}, abstractNote={To date, only a limited number of creep studies have been carried out on nanocrystalline materials. These studies have remained largely inconclusive in establishing the creep mechanisms in nanocrystalline materials. The stress exponent and activation energy values obtained for nanocrystalline materials do not correlate well with conventional, well established creep models. Furthermore, discrepancy between experimentally determined deformation rates and theoretical predictions suggests that an entirely new mechanism of creep may be operational in these materials. Thus, this work aims to develop an understanding of the creep behavior of nanocrystalline materials by considering a stress assisted grain growth mechanism that has been recently identified in these materials. A model that provides an understanding of some observations made in creep literature has been developed. Impression creep data obtained from tests on nanocrystalline aluminum agree with model predictions.}, number={21-22}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Gollapudi, S. and Rajulapati, K. V. and Charit, I. and Koch, C. C. and Scattergood, R. O. and Murty, K. L.}, year={2010}, month={Aug}, pages={5773–5781} }
 @article{wu_youssef_koch_mathaudhu_kecskes_zhu_2011, title={Deformation twinning in a nanocrystalline hcp Mg alloy}, volume={64}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2010.10.024}, abstractNote={Nanocrystalline (nc) hexagonal close-packed (hcp) metals are rarely observed to deform by twinning, which is contrary to face-centered cubic metals. Here we report that, after alloying Mg with 10 at.% Ti, deformation twins are observed in an nc Mg–Ti alloy processed by mechanical attrition. The formation of deformation twins is attributed to the alloying effect, which may change the energy path for twinning. These results point to a promising approach to design nc hcp alloys for superior mechanical properties.}, number={3}, journal={SCRIPTA MATERIALIA}, author={Wu, X. L. and Youssef, K. M. and Koch, C. C. and Mathaudhu, S. N. and Kecskes, L. J. and Zhu, Y. T.}, year={2011}, month={Feb}, pages={213–216} }
 @article{gupta_singh raman_koch_2010, title={Fabrication and oxidation resistance of nanocrystalline Fe10Cr alloy}, volume={45}, ISSN={0022-2461 1573-4803}, url={http://dx.doi.org/10.1007/s10853-010-4665-3}, DOI={10.1007/s10853-010-4665-3}, number={17}, journal={Journal of Materials Science}, publisher={Springer Science and Business Media LLC}, author={Gupta, Rajeev K. and Singh Raman, R. K. and Koch, Carl C.}, year={2010}, month={Jun}, pages={4884–4888} }
 @article{koch_scattergood_youssef_chan_zhu_2010, title={Nanostructured materials by mechanical alloying: new results on property enhancement}, volume={45}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-010-4252-7}, number={17}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Koch, Carl C. and Scattergood, Ronald O. and Youssef, Khaled M. and Chan, Ethan and Zhu, Yuntian T.}, year={2010}, month={Sep}, pages={4725–4732} }
 @article{vanleeuwen_darling_koch_scattergood_2011, title={Novel technique for the synthesis of ultra-fine porosity metal foam via the inclusion of condensed argon through cryogenic mechanical alloying}, volume={528}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2010.11.057}, abstractNote={It was discovered that mechanical milling of metal powders in an ultra high purity argon atmosphere at cryogenic temperatures can result in argon being incorporated into the metal. This incorporated argon causes expansion by increasing the porosity when the material is annealed. The resulting annealed material can be classified as metal foam due to its highly porous nature. The most porous samples were measured to have nearly 50% porosity. This effect was observed in nominally pure copper and an alloy of 81 at% palladium and 19 at% zirconium.}, number={4-5}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={VanLeeuwen, Brian K. and Darling, Kristopher A. and Koch, Carl C. and Scattergood, Ron O.}, year={2011}, month={Feb}, pages={2192–2195} }
 @article{raman_gupta_koch_2010, title={Resistance of nanocrystalline vis-a-vis microcrystalline Fe-Cr alloys to environmental degradation and challenges to their synthesis}, volume={90}, ISSN={["1478-6443"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77954082488&partnerID=MN8TOARS}, DOI={10.1080/14786435.2010.484402}, abstractNote={This paper presents a hypothesis and its experimental validation that a nanostructure can bring about dramatic improvements in the oxidation/corrosion resistance of iron–chromium alloys. More specifically, a nanocrystalline Fe–10 wt% Cr alloy was found to undergo oxidation at a rate that was an order of magnitude lower than its microcrystalline counterpart. Importantly, the oxidation resistance of nanocrystalline Fe–10 wt% Cr alloy was comparable with that of the common corrosion-resistant microcrystalline stainless steels (having 18–20 wt% chromium). The findings have the potential of leading to the next generation of oxidation-resistant alloys. However, due to poor thermal stability of nanocrystalline structure, synthesis/processing of such alloys is a challenge. Discs of nanocrystalline Fe–10% Cr alloy were produced by ball-milling of Fe and Cr powders and compaction of the powder without considerable grain growth by processing within a suitable time–temperature window. The paper also presents a theoretical treatise to arrive at the minimum chromium content required for establishing a protective layer of chromium oxide in an Fe–Cr alloy of a given nanometric grain size.}, number={23}, journal={PHILOSOPHICAL MAGAZINE}, author={Raman, R. K. Singh and Gupta, Rajeev K. and Koch, Carl C.}, year={2010}, pages={3233–3260} }
 @article{darling_vanleeuwen_koch_scattergood_2010, title={Thermal stability of nanocrystalline Fe-Zr alloys}, volume={527}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2010.02.043}, abstractNote={Fe–Zr nanocrystalline alloys with an as-milled grain size less than 10 nm were synthesized by ball milling. The microstructure changes due to annealing were characterized using X-ray line broadening, microhardness, focused ion beam channeling contrast imaging, and transmission electron microscopy (TEM). Additions of 1/3 to 4 at.% Zr stabilized nanocrystalline grain sizes at elevated annealing temperatures compared to pure Fe. With 4 at.% Zr, a fully nanocrystalline microstructure with a TEM grain size of 52 nm was retained at temperatures in excess of 900 °C. Alloys with lower Zr contents showed less stability, but still significant compared to pure Fe. Bimodal nano–micro grain size microstructures were also observed.}, number={15}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Darling, K. A. and VanLeeuwen, B. K. and Koch, C. C. and Scattergood, R. O.}, year={2010}, month={Jun}, pages={3572–3580} }
 @article{vanleeuwen_darling_koch_scattergood_butler_2010, title={Thermal stability of nanocrystalline Pd81Zr19}, volume={58}, ISSN={["1359-6454"]}, DOI={10.1016/j.actamat.2010.04.023}, abstractNote={Grain growth stability in mechanically alloyed nanocrystalline Pd81Zr19 was investigated. Previous research suggested that the alloy is thermodynamically stable to very high temperatures. When X-ray diffraction (XRD) is used to estimate the grain size of annealed samples the alloy appears to have remarkable resistance to growth. Microscopy done here on the same alloy indicated that the XRD estimates are not accurate for samples annealed above 600 °C. It appears that when this alloy is annealed at high temperatures XRD peak broadening is retained for reasons that are unrelated to the grain size. The alloy still has much improved grain growth stability compared with pure Pd, but not as significant as suggested by the XRD results. A similar phenomenon was observed in Fe–Zr alloys.}, number={12}, journal={ACTA MATERIALIA}, author={VanLeeuwen, Brian K. and Darling, Kristopher A. and Koch, Carl C. and Scattergood, Ron O. and Butler, Brady G.}, year={2010}, month={Jul}, pages={4292–4297} }
 @article{gollapudi_rajulapati_charit_youssef_koch_scattergood_murty_2010, title={Understanding creep in nanocrystalline materials}, volume={63}, ISSN={["0975-1645"]}, DOI={10.1007/s12666-010-0050-9}, number={2-3}, journal={TRANSACTIONS OF THE INDIAN INSTITUTE OF METALS}, author={Gollapudi, S. and Rajulapati, K. V. and Charit, I. and Youssef, K. M. and Koch, C. C. and Scattergood, R. O. and Murty, K. L.}, year={2010}, month={Apr}, pages={373–378} }
 @article{gobien_scattergood_goodwin_koch_2009, title={Mechanical behavior of bulk ultra-fine-grained Zn-Al die-casting alloys}, volume={518}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2009.04.023}, abstractNote={The mechanical properties of Zn–4 wt% Al casting alloys are compared after various processing methods including sand casting, die-casting, and high energy cryogenic ball milling. For the cast structures there is an increase in strength when transitioning from a coarse sand casting microstructure to a finer grained thin-section die-casting. This is in contrast to a decrease in strength and increase in ductility seen when the cast structure is broken up by high energy cryogenic ball milling to a uniform ultra-fine grain scale. The ultra-fine grained structures produced by cryogenic ball milling subjected to a range of isothermal heat treatments follow the Hall–Petch behavior over the range of grain sizes studied.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Gobien, J. M. and Scattergood, R. O. and Goodwin, F. E. and Koch, C. C.}, year={2009}, month={Aug}, pages={84–88} }
 @article{li_misra_zhu_horita_koch_holesinger_2009, title={Processing and characterization of nanostructured Cu-carbon nanotube composites}, volume={523}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2009.05.031}, abstractNote={Carbon nanotube (CNT) reinforced nanostructured Cu matrix composite with a grain size less than 25 nm has been successfully fabricated via a combination of ball milling and high-pressure torsion. CNTs were found to be homogeneously dispersed into the metal matrix, leading to grain refinement with a narrow grain size distribution and significant increase in hardness.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Li, Hongqi and Misra, Amit and Zhu, Yuntian and Horita, Zenji and Koch, Carl C. and Holesinger, Terry G.}, year={2009}, month={Oct}, pages={60–64} }
 @article{li_misra_horita_koch_mara_dickerson_zhu_2009, title={Strong and ductile nanostructured Cu-carbon nanotube composite}, volume={95}, ISSN={["1077-3118"]}, DOI={10.1063/1.3211921}, abstractNote={Nanocrystalline carbon nanotube (CNT)—reinforced Cu composite (grain size <25 nm) with high strength and good ductility was developed. Pillar testing reveals that its strength and plastic strain could be as large as 1700 MPa and 29%, respectively. Compared with its counterpart made under the same condition, an addition of 1 wt % CNTs leads to a dramatic increase in strength, stiffness and toughness without a sacrifice in ductility. Microstructural analysis discloses that in the Cu matrix, CNTs could be distributed either at grain boundaries or inside grains and could inhibit dislocation nucleation and motion, resulting in an increase in the strength.}, number={7}, journal={APPLIED PHYSICS LETTERS}, author={Li, Hongqi and Misra, Amit and Horita, Zenji and Koch, Carl C. and Mara, Nathan A. and Dickerson, Patricia O. and Zhu, Yuntian}, year={2009}, month={Aug} }
 @article{zhang_koch_scattergood_2009, title={The role of new particle surfaces in synthesizing bulk nanostructured metallic materials by powder metallurgy}, volume={516}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2009.03.024}, abstractNote={The role of new particle surfaces in synthesizing bulk nanostructured metallic materials by consolidation of nanostructured powders and nanopowders is analysed by developing three simple mathematical equations for calculating the α factor for different thermomechanical powder consolidation processes such as hot pressing, high pressure torsion and extrusion. The α factor is the fraction of the area of the powder particle surfaces newly formed during consolidation over the total particle surface area which includes both pre-existing surface area and the newly formed surface area. It is demonstrated that the values of the α factor calculated using these equations can be reasonably used to predict the level of inter-particle atomic bonding that is likely to be achieved through cold-welding by the above mentioned typical thermomechanical powder consolidation processes which also include high energy mechanical milling. Based on this analysis, it is clear that uniaxial hot pressing of a powder compact in a rigid die at low homologous temperatures (<0.5Tm) is unlikely to be capable of achieving a sufficiently high level of inter-particle atomic bonding for producing a high quality consolidated material, while processes involving a large amount of plastic deformation have such capabilities.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Zhang, D. L. and Koch, C. C. and Scattergood, R. O.}, year={2009}, month={Aug}, pages={270–275} }
 @article{gupta_raman_koch_2008, title={Grain growth behaviour and consolidation of ball-milled nanocrystalline Fe-10Cr alloy}, volume={494}, ISSN={["0921-5093"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-49849092043&partnerID=MN8TOARS}, DOI={10.1016/j.msea.2008.04.019}, abstractNote={Nanocrystalline iron–chromium alloys may provide considerable corrosion resistance, even at low chromium contents. However, processing of such alloys could be a challenge. This paper describes successful synthesis of nanocrystalline Fe–10%Cr alloy by ball-milling route. In the absence of suitable hot compaction facility, the alloy powder could be successfully compacted close to the desired density, by employing a step of prior annealing of the powder. Grain growth behaviour of Fe–10%Cr nanocrystalline alloy was investigated at 500, 600 and 700 °C. At 500 °C, no appreciable grain growth was observed, after the initial grain growth. However, sudden and rapid grain growth was observed after 90 min at 600 °C, and 30 min at 700 °C.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Gupta, Rajeev and Raman, R. K. Singh and Koch, Carl C.}, year={2008}, month={Oct}, pages={253–256} }
 @article{darling_chan_wong_semones_scattergood_koch_2008, title={Grain-size stabilization in nanocrystalline FeZr alloys}, volume={59}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2008.04.045}, abstractNote={Nanocrystalline Fe–Zr alloys with a nominal grain size of 10 nm were synthesized by mechanical alloying. The grain size in pure Fe was >200 nm after annealing for 1 h at T/TM = 0.5. Additions of 1 at.% Zr stabilized the grain size at 50 nm up to T/TM = 0.92. Particle pinning, solute drag and reduction in grain-boundary energy have been proposed as stabilization mechanisms. The stabilization in Fe–Zr alloys is attributed to a reduction in grain-boundary energy due to Zr segregation.}, number={5}, journal={SCRIPTA MATERIALIA}, author={Darling, Kris A. and Chan, Ryan N. and Wong, Patrick Z. and Semones, Jonathan E. and Scattergood, Ronald O. and Koch, Carl C.}, year={2008}, month={Sep}, pages={530–533} }
 @article{youssef_koch_fedkiw_2008, title={Influence of pulse plating parameters on the synthesis and preferred orientation of nanocrystalline zinc from zinc sulfate electrolytes}, volume={54}, ISSN={["1873-3859"]}, DOI={10.1016/j.electacta.2008.07.048}, abstractNote={The influence of pulse electrodeposition parameters (current on-time Ton, current off-time Toff, and pulse current density Jp) was investigated on the surface morphology and grain size of zinc electrodeposited from a sulfate bath containing polyacrylamide and thiourea additives. The grain size and surface morphology of zinc deposits were studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), and the preferred orientation of the deposits was studied by X-ray diffraction. At constant current off-time and pulse current density, the grain size decreased asymptotically with increasing current on-time. In contrast, increase in the current off-time at constant current on-time and pulse current density resulted in grain growth. A progressive decrease of the grain size was observed with increasing pulse current density at constant current on-time and off-time. Nanocrystalline zinc with an average grain size of 38 nm was obtained at a pulse current density of 1200 mA/cm2. The crystallographic orientations developed were correlated with the change in the cathodic overpotential, the angle between the preferred oriented plane and the lowest energy of formation plane (0 0 0 2), and the pulse electrodeposition parameters.}, number={2}, journal={ELECTROCHIMICA ACTA}, author={Youssef, K. M. and Koch, C. C. and Fedkiw, P. S.}, year={2008}, month={Dec}, pages={677–683} }
 @article{rajulapati_scattergood_murty_horita_langdon_koch_2008, title={Mechanical properties of bulk nanocrystalline aluminum-tungsten alloys}, volume={39A}, ISSN={["1073-5623"]}, DOI={10.1007/s11661-008-9593-3}, number={10}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Rajulapati, K. V. and Scattergood, R. O. and Murty, K. L. and Horita, Z. and Langdon, T. G. and Koch, C. C.}, year={2008}, month={Oct}, pages={2528–2534} }
 @article{darling_reynolds_leonard_duscher_scattergood_koch_2008, title={Self-assembled three-dimensional Cu-Ge nanoweb composite}, volume={19}, ISSN={["1361-6528"]}, DOI={10.1088/0957-4484/19/13/135603}, abstractNote={The inexpensive combination of cryogenically milled Cu3Ge powders sonochemically processed in a standard ultrasonic cleaner has led to the prototype of a heretofore undescribed class of material. This prototype is a nanostructured composite composed of 4.5 nm diameter Cu nanocrystals embedded in a three-dimensional (3D) amorphous CuGeO3 polyhedron web matrix. The diameters of the wires comprising the matrix are typically 5–15 nm. Complete structural and compositional characterization is reported to provide additional insight and firm designation on the observation of this previously undescribed class of material. The large surface to volume ratio of these nanoweb composites may offer unique advantages based on altered optical or electronic and magnetic properties. For example, quantum confinement of the Cu dots in the amorphous 3D nanowebs is possible. Nanostructures in general have altered properties compared to those of bulk materials and the same is expected in nanostructured composites.}, number={13}, journal={NANOTECHNOLOGY}, author={Darling, Kris A. and Reynolds, C. Lewis, Jr. and Leonard, Donovan N. and Duscher, Gerd and Scattergood, Ronald O. and Koch, Carl C.}, year={2008}, month={Apr} }
 @article{koch_scattergood_darling_semones_2008, title={Stabilization of nanocrystalline grain sizes by solute additions}, volume={43}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-008-2870-0}, number={23-24}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Koch, C. C. and Scattergood, R. O. and Darling, K. A. and Semones, J. E.}, year={2008}, month={Dec}, pages={7264–7272} }
 @article{scattergood_koch_murty_brenner_2008, title={Strengthening mechanisms in nanocrystalline alloys}, volume={493}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2007.04.132}, abstractNote={The mechanisms for strengthening nanocrystalline metals by alloy additions are reviewed and a new model for nano-particle strengthening by Orowan bypassing in nano-grains is proposed. Recent experimental results for three different nanocrystalline alloy systems, Fe–Pb, Fe–Al2O3 and Al–Pb are presented and analyzed in terms of non-equilibrium solid solution strengthening, nano-composite strengthening and Orowan particle strengthening, respectively. Conflicting alloy hardening and softening effects observed in Al–Pb appear to be the result of interplay between Orowan particle hardening and a softening mechanism due to grain-boundary segregation. Preliminary MD simulations support the latter suggestion.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Scattergood, R. O. and Koch, C. C. and Murty, K. L. and Brenner, D.}, year={2008}, month={Oct}, pages={3–11} }
 @article{darling_guduru_reynolds_bhosle_chan_scattergood_koch_narayan_aboelfotoh_2008, title={Thermal stability, mechanical and electrical properties of nanocrystalline Cu3Ge}, volume={16}, ISSN={0966-9795}, url={http://dx.doi.org/10.1016/j.intermet.2007.11.005}, DOI={10.1016/j.intermet.2007.11.005}, abstractNote={The intermetallic ɛ1 compound Cu3Ge was produced through a mechanical alloying procedure that enables the formation of a nanograined microstructure. There is a dependence of grain size (20–11 nm) on milling conditions. The microstructure remained very stable even at temperatures up to 500 °C for 5 h which is a minimum of 76% of the melting temperature. The materials produced by these methods were in the form of powders with particle size ranging from 200 nm to 10 μm. The morphology of the particles varied with the largest being rough and irregular and the smallest being spherical. Preliminary resistivity measurements showed low resistivity, 8.8 μΩ cm, which is comparable to that previously reported for thin films with grain sizes thousands of times larger. Nanoindentation was also performed, yielding an elastic modulus of ∼110 GPa.}, number={3}, journal={Intermetallics}, publisher={Elsevier BV}, author={Darling, Kris A. and Guduru, R.K. and Reynolds, C. Lewis, Jr and Bhosle, Vikram M. and Chan, Ryan N. and Scattergood, Ronald O. and Koch, Carl C. and Narayan, J. and Aboelfotoh, M.O.}, year={2008}, month={Mar}, pages={378–383} }
 @article{guduru_wong_darling_koch_murty_scattergood_2007, title={Determination of Activation Volume in Nanocrystalline Cu Using the Shear Punch Test}, volume={9}, ISSN={1438-1656 1527-2648}, url={http://dx.doi.org/10.1002/adem.200700181}, DOI={10.1002/adem.200700181}, abstractNote={The mechanical behavior of nanocrystalline metals has been a research topic of interest for the past two decades. The current understanding is summarized in several recent reviews. Researchers have been investigating the deformation mechanisms in nanocrystalline metals and alloys through experimental and modeling routes. Modeling results indicate that there is a transition from dislocation generation at sources within grains to grain-boundary mediated dislocation generation in the grain size range between about 100 to 10 nm. Below 10 nm, grain boundary deformation modes (sliding, rotation, etc.) become dominant and inverse Hall-Petch effects have been reported. Experimental evidence to confirm these predictions is an active area of research. Two important experimental parameters that are useful in characterizing the deformation kinetics of materials are the strain rate sensitivity m and the activation volume V*. 11, 12] These are related by m = kT/V*r where k is Boltzmann’s constant, T is temperature (K) and r is the stress. There is a limited amount of data available on m and V* measurements for nanocrystalline metals. 5, 11–14] One aspect of this is the fact that research-scale synthesizing techniques often produce small quantities of material and mechanical testing procedures suited to small sample sizes are required. 5, 7, 13–18] In addition to this fact there is a tremendous scarcity of testing methodologies for testing the materials at small scales such as Micro-Electro-Mechanical-Systems (MEMS) where micro tensile and nanoindentation tests are used for understanding the deformation behaviour. 20] The aim of the present work was to extend the shear punch test (SPT) technique to the measurement of activation volumes on small scale specimens of few millimeters (∼ 1 mm to 3 mm). The advantage of SPT over nanoindentation and micro tensile tests is the deformation zone where a large number of grains undergo deformation within the shear zone and overcomes the problem of strain gradient plasticity effects, gain size effects as well as the specimen size effects. The SPT has been used for evaluating the yield and ultimate stress by numerous researchers, including us. The SPT shear yield or ultimate strength value s can be correlated with its tensile test counterpart r using the relation r = as. The correlation factor a depends upon the testing setup and data analysis methods. The Von Mises (VM) yield criterion predicts a = 3 if the SPT approximates pure shear loading conditions. This was the case in where the details and standardization of the SPT technique used in the present research work are given. The stress relaxation method has been used to determine activation volumes and dislocation dynamics in coarse-grain metals and alloys and in nanocrystalline Ni. The tests are normally done using uniaxial loading conditions. In the present study, we use the stress relaxation method in conjunction with the SPT technique. As far as we are aware, this is the first time that the full implementation of this method has been reported.}, number={10}, journal={Advanced Engineering Materials}, publisher={Wiley}, author={Guduru, R. K. and Wong, P. Z. and Darling, K. A. and Koch, C. C. and Murty, K. L. and Scattergood, R. O.}, year={2007}, month={Oct}, pages={855–859} }
 @article{guduru_murty_youssef_scattergood_koch_2007, title={Mechanical behavior of nanocrystalline copper}, volume={463}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2006.07.165}, DOI={10.1016/j.msea.2006.07.165}, abstractNote={The mechanical behavior of nanocrystalline materials has been studied extensively for the past few years. Recent studies on artifact-free materials with nanosize grains less than 100 nm have been very fruitful. These nanograined metals have exhibited very high strengths with reasonably good ductility. While there have been a large number of studies on hardness and strength characteristics, studies on strain rate sensitivity (SRS) are very limited. We describe here some of our recent work in characterizing SRS as well as activation volumes of nanograined copper using different testing procedures. These tests have been carried out under iso-strain rate and iso-structural conditions.}, number={1-2}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Guduru, Ramesh K. and Murty, K. Linga and Youssef, Khaled M. and Scattergood, Ronald O. and Koch, Carl C.}, year={2007}, month={Aug}, pages={14–21} }
 @article{guduru_darling_scattergood_koch_murty_2007, title={Mechanical properties of electrodeposited nanocrystalline copper using tensile and shear punch tests}, volume={42}, ISSN={["0022-2461"]}, DOI={10.1007/s10853-006-1095-3}, number={14}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Guduru, Ramesh Kumar and Darling, Kristopher A. and Scattergood, Ronald O. and Koch, Carl C. and Murty, K. L.}, year={2007}, month={Jul}, pages={5581–5588} }
 @article{koch_2007, title={Structural nanocrystalline materials: an overview}, volume={ 42}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-006-0609-3}, number={5}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Koch, Carl C.}, year={2007}, month={Mar}, pages={1403–1414} }
 @article{koch_scattergood_murty_2007, title={The mechanical behavior of multiphase nanocrystalline materials}, volume={59}, ISSN={["1047-4838"]}, DOI={10.1007/s11837-007-0042-3}, number={3}, journal={JOM}, author={Koch, Carl C. and Scattergood, Ronald O. and Murty, K. L.}, year={2007}, month={Mar}, pages={66–70} }
 @article{guduru_nagasekhar_scattergood_koch_murty_2007, title={Thickness and clearance effects in shear punch testing}, volume={9}, ISSN={["1438-1656"]}, DOI={10.1002/adem.200600255}, abstractNote={Shear punch testing (SPT) is a miniaturized specimen testing technique and is often used to predict the tensile properties of metals and alloys by testing a small amount of material. In order to rationalize the testing methodology it is necessary to understand the effect of different testing procedure parameters such as specimen thickness and die-punch clearance on the evaluated mechanical properties. We present our understanding of the above parameters on the SPT yield strength using finite element modeling studies in conjunction with our previous experimental results.}, number={3}, journal={ADVANCED ENGINEERING MATERIALS}, author={Guduru, Ramesh K. and Nagasekhar, Anumalasetty V. and Scattergood, Ronald O. and Koch, Carl C. and Murty, Korukonda L.}, year={2007}, month={Mar}, pages={157–160} }
 @article{rajulapati_scattergood_murty_duscher_koch_2006, title={Effect of Pb on the mechanical properties of nanocrystalline Al}, volume={55}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2006.03.051}, abstractNote={Nanocrystalline (nc) Al–Pb two phase mixtures of different Pb concentrations were made by two different routes using high energy ball milling. The microhardness measurements show a softening in nc Al–Pb composites with the increase in Pb content, contradicting the previous results reported in the literature. We conclude that interaction of Pb atoms with nanocrystalline Al grain boundaries is responsible for the softening of the nc Al matrix observed in the current study.}, number={2}, journal={SCRIPTA MATERIALIA}, author={Rajulapati, Koteswararao V. and Scattergood, Ronald O. and Murty, Korukonda L. and Duscher, Gerd and Koch, Carl C.}, year={2006}, month={Jul}, pages={155–158} }
 @article{guduru_nagasekhar_scattergood_koch_murty_2006, title={Finite element analysis of a shear punch test}, volume={37A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-006-0092-0}, number={5}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Guduru, R. K. and Nagasekhar, A. V. and Scattergood, R. O. and Koch, C. C. and Murty, K. L.}, year={2006}, month={May}, pages={1477–1483} }
 @article{guduru_scattergood_koch_murty_guruswamy_mccarter_2006, title={Mechanical properties of nanocrystalline Fe-Pb and Fe-Al2O3}, volume={54}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2006.02.014}, abstractNote={Fe, Fe–Al2O3, and Fe–Pb nanocrystalline alloys were prepared using ball milling. Fe–Al2O3 forms a nanocomposite and rule-of-mixtures hardening occurs with an additional contribution due to grain size reduction during milling. Fe–Pb forms a non-equilibrium solid solution where hardening appears to be modulated by Pb clustering and segregation to grain boundaries.}, number={11}, journal={SCRIPTA MATERIALIA}, author={Guduru, RK and Scattergood, RO and Koch, CC and Murty, KL and Guruswamy, S and McCarter, MK}, year={2006}, month={Jun}, pages={1879–1883} }
 @article{guduru_darling_scattergood_koch_murty_bakkal_shih_2006, title={Shear punch tests for a bulk metallic glass}, volume={14}, ISSN={["1879-0216"]}, DOI={10.1016/j.intermet.2006.01.052}, abstractNote={A shear punch test technique was used for characterization of the mechanical properties of Zr–5Ti–17.9Cu–14.6Ni–10Al bulk metallic glass. The ultimate shear stress values matched very closely with values derived from uniaxial compression tests reported in the literature. This is consistent with a lack of pressure sensitivity in compression reported for this particular metallic glass. Deformation response was strain rate insensitive up to a critical rate, beyond which softening occurred. The latter was attributed to thermal heating effects.}, number={12}, journal={INTERMETALLICS}, author={Guduru, R. K. and Darling, K. A. and Scattergood, R. O. and Koch, C. C. and Murty, K. L. and Bakkal, M. and Shih, A. J.}, year={2006}, month={Dec}, pages={1411–1416} }
 @article{trichy_scattergood_koch_murty_2005, title={Ball indentation tests for a Zr-based bulk metallic glass}, volume={53}, ISSN={["1872-8456"]}, DOI={10.1016/j.scriptamat.2005.08.010}, abstractNote={Zr52.5Ti5Cu17.9Ni14.6Al10 bulk metallic glass was characterized using ball indentation tests. Comparison of the data with the expanding cavity model revealed that the deformation is pressure insensitive for compressive loading. The plastic flow curves obtained from indentation tests showed perfectly plastic response and no strain rate sensitivity up to 15% strain.}, number={12}, journal={SCRIPTA MATERIALIA}, author={Trichy, GR and Scattergood, RO and Koch, CC and Murty, KL}, year={2005}, month={Dec}, pages={1461–1465} }
 @article{koch_youssef_scattergood_murty_2005, title={Breakthroughs in Optimization of Mechanical Properties of Nanostructured Metals and Alloys}, volume={7}, ISSN={1438-1656 1527-2648}, url={http://dx.doi.org/10.1002/adem.200500094}, DOI={10.1002/adem.200500094}, abstractNote={AbstractWhile nanocrystalline metals can have strength and hardness values factors of 10 or more greater than their conventional grain size counterparts, ductility in tension has been disappointing, typically less than 2% elongation. This paper reviews the limitations to ductility in nanocrystalline materials and presents the results of recent breakthroughs wherein both high strength and good ductility are observed.}, number={9}, journal={Advanced Engineering Materials}, publisher={Wiley}, author={Koch, C. C. and Youssef, K. M. and Scattergood, R. O. and Murty, K. L.}, year={2005}, month={Sep}, pages={787–794} }
 @article{koch_youssef_scattergood_murty_2005, title={Breakthroughs in optimization of mechanical properties of nanostructured metals and alloys}, volume={7}, DOI={10.1002/adern.200500094}, number={9}, journal={Advanced Engineering Materials}, author={Koch, C. C. and Youssef, K. M. and Scattergood, R. O. and Murty, K. L.}, year={2005}, pages={787–794} }
 @article{zhang_raynova_koch_scattergood_youssef_2005, title={Consolidation of a Cu-2.5 vol.% Al2O3 powder using high energy mechanical milling}, volume={410}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2005.08.109}, abstractNote={Abstract In situ consolidation of a Cu–2.5 vol.% Al 2 O 3 powder by high energy ball milling has been studied by examining changes of size, morphology, macrostructure and microstructure of the powder particles, lumps, and balls formed with increasing milling time under different conditions. This study clearly demonstrates that the consolidation of the Cu–2.5 vol.% Al 2 O 3 powder by high energy ball milling is accomplished initially by coalescence of powder particles through cold welding which leads to formation of lumps, then by cold welding and re-shaping of the lumps into small balls, and finally by cold welding of small balls into larger balls. The maximum diameter of the large balls is comparable with the diameter of the milling balls used as a milling medium. The two types of defects in the consolidated lumps and balls in the large balls, concentrated voids and crack-like voids, show that the material undergoes a large amount of plastic flow during the process of consolidation. The consolidation of the Cu–2.5 vol.% Al 2 O 3 powder can also been achieved by a combination of cryomilling and room temperature milling, but the consolidation process is slower due to increased hardness of the powder particles. The study also shows that the Al 2 O 3 fine particles are incorporated into the Cu matrix forming a composite structure when the lumps are formed, and the large balls exhibit a nanostructure with grain sizes smaller than 100 nm.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Zhang, DL and Raynova, S and Koch, CC and Scattergood, RO and Youssef, KM}, year={2005}, month={Nov}, pages={375–380} }
 @article{guduru_darling_kishore_scattergood_koch_murty_2005, title={Evaluation of mechanical properties using shear–punch testing}, volume={395}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2004.12.048}, DOI={10.1016/j.msea.2004.12.048}, abstractNote={The evaluation of mechanical properties like yield and ultimate tensile strengths from shear–punch tests is important when the availability of material is limited. A shear–punch test setup was built in our laboratory and the mechanical properties for different materials; mild steel, pure Al, Zn, brass (Cu–30% Zn by wt.), Al 6061, Austenitic and Martensitic stainless steels were evaluated. A new method using 1% offset criterion in conjunction with normalized shear–punch curves was used to measure the shear yield strength. A linear correlation between the shear data and tensile data was established for yield and ultimate strengths. The variation of the yield and ultimate shear strength was studied as a function of the sample thickness and die–punch clearance for soft, medium and high strength materials.}, number={1-2}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={Guduru, R.K. and Darling, K.A. and Kishore, R. and Scattergood, R.O. and Koch, C.C. and Murty, K.L.}, year={2005}, month={Mar}, pages={307–314} }
 @article{youssef_scattergood_murty_koch_2006, title={Nanocrystalline Al-Mg alloy with ultrahigh strength and good ductility}, volume={54}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2005.09.028}, abstractNote={A bulk nanocrystalline Al–5%Mg alloy was synthesized by an in situ consolidation mechanical alloying technique. The mechanical behavior of this alloy was investigated by hardness and tensile tests, which revealed it has four times the strength of a conventional Al-5083 alloy along with good ductility (8.5% elongation). The microstructure was investigated by X-ray diffraction and transmission electron microscopy, and the fracture surface by scanning electron microscopy.}, number={2}, journal={SCRIPTA MATERIALIA}, author={Youssef, KM and Scattergood, RO and Murty, KL and Koch, CC}, year={2006}, month={Jan}, pages={251–256} }
 @article{cheng_ma_wang_kecskes_youssef_koch_trociewitz_han_2005, title={Tensile properties of in situ consolidated nanocrystalline Cu}, volume={53}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2004.12.005}, abstractNote={We have prepared Cu powders with nanocrystalline grain sizes via ball milling at liquid nitrogen temperature. An in situ consolidation technique was used to produce fully dense nanocrystalline Cu samples centimeters in lateral dimensions and about one millimeter in thickness. We report a much improved combination of tensile strength and ductility, over the tensile properties of other nanocrystalline Cu materials documented in the literature. We also demonstrate the elevated strain rate sensitivity and strong temperature dependence of the flow stress and explain the results in terms of the thermally activated deformation mechanisms operative in the nanocrystalline grains. The nearly perfectly plastic behavior and shear localization observed are discussed and compared with the strain hardening behavior and deformation modes known for other nanocrystalline metals.}, number={5}, journal={ACTA MATERIALIA}, author={Cheng, S and Ma, E and Wang, YM and Kecskes, LJ and Youssef, KM and Koch, CC and Trociewitz, UP and Han, K}, year={2005}, month={Mar}, pages={1521–1533} }
 @article{youssef_scattergood_murty_horton_koch_2005, title={Ultrahigh strength and high ductility of bulk nanocrystalline copper}, volume={87}, ISSN={["1077-3118"]}, DOI={10.1063/1.2034122}, abstractNote={We have synthesized artifact-free bulk nanocrystalline copper samples with a narrow grain size distribution (mean grain size of 23nm) that exhibited tensile yield strength about 11 times higher than that of conventional coarse-grained copper, while retaining a 14% uniform tensile elongation. In situ dynamic straining transmission electron microscope observations of the nanocrystalline copper are also reported, which showed individual dislocation motion and dislocation pile-ups. This suggests a dislocation-controlled deformation mechanism that allows for the high strain hardening observed. Trapped dislocations are observed in the individual nanograins.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Youssef, KM and Scattergood, RO and Murty, KL and Horton, JA and Koch, CC}, year={2005}, month={Aug} }
 @article{youssef_koch_fedkiw_2004, title={Influence of additives and pulse electrodeposition parameters on production of nanocrystalline zinc from zinc chloride electrolytes}, volume={151}, ISSN={["1945-7111"]}, DOI={10.1149/1.1636739}, abstractNote={Pulse electrodeposition was used to produce nanocrystalline zinc from an aqueous zinc chloride electrolyte with polyacrylamide and thiourea as additives. The influence of additive concentration and pulse electrodeposition parameters, namely, current-on time, current-off time, and peak current density on the grain size, surface morphology, and preferred orientation was investigated. The grain size and surface morphology of zinc deposits were studied by scanning electron microscopy and field emission scanning electron microscopy. The preferred orientation of zinc deposits was studied by X-ray diffraction. The optimum concentrations of polyacrylamide and thiourea in the bath that give the finest grains were 0.7 and 0.05 g/L, respectively. At constant current-off time and peak current density, the grain size decreased asymptotically with increasing current-on time. An increase in the current-off time at constant current-on time and peak current density resulted in grain growth. A progressive decrease of the grain size was observed with increasing peak current density at constant current-on and -off time. Nanocrystalline zinc with an average grain size of 50 nm was obtained at a peak current density of 1000 mA/cm 2 . The crystal orientations developed were correlated to the variation in the cathode overpotential accompanied with changing the electrodeposition parameters. A (1013) preferred orientation was developed at low overpotential while higher overpotential developed a dual (1122) (1010) orientation.}, number={2}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Youssef, KMS and Koch, CC and Fedkiw, PS}, year={2004}, month={Feb}, pages={C103–C111} }
 @article{youssef_scattergood_murty_koch_2004, title={Ultratough nanocrystalline copper with a narrow grain size distribution}, volume={85}, ISSN={["1077-3118"]}, DOI={10.1063/1.1779342}, abstractNote={We report a unique way of using mechanical milling/in situ consolidation at both liquid-nitrogen and room temperature to produce artifact-free nanocrystalline Cu(23nm) with a narrow grain size distribution. This nanocrystalline Cu exhibits an extraordinarily high yield strength (770MPa), as predicted from a Hall–Petch extrapolation, along with good ductility (comparable with ∼30% uniform tensile elongation). Possible factors leading to this excellent optimization of strength and ductility are discussed.}, number={6}, journal={APPLIED PHYSICS LETTERS}, author={Youssef, KM and Scattergood, RO and Murty, KL and Koch, CC}, year={2004}, month={Aug}, pages={929–931} }
 @article{youssef_koch_fedkiw_2004, title={Improved corrosion behavior of nanocrystalline zinc produced by pulse-current electrodeposition}, volume={46}, ISSN={["1879-0496"]}, DOI={10.1016/S0010-938X(03)00142-2}, abstractNote={Pulse electrodeposition was used to produce nanocrystalline (nc) zinc from zinc chloride electrolyte with polyacrylamide and thiourea as additives. Field emission scanning electron microscopy (FESEM) was used to study the grain size and surface morphology of the deposits and X-ray diffraction was used to examine their preferred orientation. Corrosion behavior of the electrodeposited nc zinc in comparison with electrogalvanized (EG) steel in de-aerated 0.5 N NaOH solution was studied using potentiodynamic polarization and impedance measurements. A scanning electron microscope (SEM) was used to characterize the surface morphology of the EG steel before corrosion testing. Surface morphologies of nc zinc deposits and EG steel were also studied after potentiondynamic polarization by SEM. Nanocrystalline zinc (56 nm) with random orientation was produced. The estimated corrosion rate of nc zinc was found to be about 60% lower than that of EG steel, 90 and 229 μA/cm2, respectively. The surface morphology of corroded nc zinc was characterized by discrete etch pits, however, uniform corrosion was obtained after potentiodynamic polarization of EG steel. The passive film formed on the nc zinc surface seems to be a dominating factor for the corrosion behavior observed.}, number={1}, journal={CORROSION SCIENCE}, author={Youssef, KMS and Koch, CC and Fedkiw, PS}, year={2004}, month={Jan}, pages={51–64} }
 @article{koch_2003, title={Optimization of strength and ductility in nanocrystalline and ultrafine grained metals}, volume={49}, ISSN={["1359-6462"]}, DOI={10.1016/S1359-6462(03)00394-4}, abstractNote={The possible optimization of strength and ductility in nanocrystalline and ultrafine grained metals is assessed. Most nanocrystalline metals show little ductility while exhibiting enhanced strength. The possibility that these properties can be optimized is discussed for microstructures with appropriate grain size distributions, and the introduction of second phase particles.}, number={7}, journal={SCRIPTA MATERIALIA}, author={Koch, CC}, year={2003}, month={Oct}, pages={657–662} }
 @article{zhu_zhang_wang_sergueeva_mukherjee_scattergood_narayan_koch_2003, title={Synthesis of bulk nanostructured Zn by combinations of cryomilling and powder consolidation by room temperature milling: optimizing mechanical properties}, volume={49}, ISSN={["1359-6462"]}, DOI={10.1016/S1359-6462(03)00297-5}, abstractNote={A new technique is used to synthesize nanocrystalline Zn, i.e. cryomilling followed by in situ consolidation of the powders by room temperature ball milling. The room temperature milling appears to sharpen the broad grain size distribution obtained by cryomilling only. Strength and ductility may be optimized in this way by the control of grain size and grain size distribution.}, number={5}, journal={SCRIPTA MATERIALIA}, author={Zhu, XK and Zhang, X and Wang, H and Sergueeva, AV and Mukherjee, AK and Scattergood, RO and Narayan, J and Koch, CC}, year={2003}, month={Sep}, pages={429–433} }
 @article{zhang_wang_scattergood_narayan_koch_2003, title={Evolution of microstructure and mechanical properties of in situ consolidated bulk ultra-fine-grained and nanocrystalline Zn prepared by ball milling}, volume={344}, ISSN={["0921-5093"]}, DOI={10.1016/s0921-5093(02)00422-7}, abstractNote={The evolution of the microstructure and mechanical properties of ultra-fine-grained and nanocrystalline Zn induced by ball milling at room temperature are studied systematically. The yield stresses measured from miniaturized disk bend tests and tensile tests are consistent with the microhardness results and generally increase with the decrease of average grain size. A dramatic decrease of hardness during milling from 1 to 3 h is a reflection of the increase of average grain size from 80 to 240 nm due to the initial unstable grain size and therefore, grain growth in this period. Young's modulus remains almost the same for samples milled for different times and is that for conventional grain size Zn. A transition from bending to membrane stretching is observed in the force–displacement curves for Zn ball milled for ≤18 h. The variation of transition strain with milling time could be related to the evolution of grain size distribution and therefore hardness during milling.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Zhang, X and Wang, H and Scattergood, RO and Narayan, J and Koch, CC}, year={2003}, month={Mar}, pages={175–181} }
 @article{zhang_wang_scattergood_narayan_koch_2002, title={Mechanical properties of cyromilled nanocrystalline Zn studied by the miniaturized disk bend test}, volume={50}, ISSN={["1359-6454"]}, DOI={10.1016/S1359-6454(02)00176-3}, abstractNote={The miniaturized disk bend test (MDBT) is useful for the study of the mechanical properties of small specimens in tension. The yield stress of cryomilled nanocrystalline Zn measured by MDBT shows periodic hardening and softening with milling time, consistent with the variation of microhardness with milling time. The periodic softening is due to the reduction of dislocation density controlled by dynamic recrystallization. The ductility of these softened nanocrystalline Zn specimens is consistently higher than that of the hardened specimens. Young's modulus shows little variation with the average grain size.}, number={13}, journal={ACTA MATERIALIA}, author={Zhang, X and Wang, H and Scattergood, RO and Narayan, J and Koch, CC}, year={2002}, month={Aug}, pages={3527–3533} }
 @article{zhang_wang_scattergood_narayan_koch_2002, title={Modulated oscillatory hardening and dynamic recrystallization in cryomilled nanocrystalline Zn}, volume={50}, ISSN={["1359-6454"]}, DOI={10.1016/S1359-6454(02)00199-4}, abstractNote={Oscillatory variation of the hardness with milling time was observed in cryomilled nanocrystalline Zn. Transmission electron microscopy showed that large variations in the dislocation density and grain-size distribution occurred during cryomilling. The observations suggest that recrystallization takes place in larger grains when the dislocation density due to strain-hardening reaches a critical level. A reaction-rate model was developed which accounts for the dynamic recrystallization effect and the observed oscillations in hardness. Good agreement was obtained with the experimental data. The results provide unique insight into grain-size effects and the interplay of these with deformation mechanisms and recrystallization effects in nanocrystalline materials.}, number={16}, journal={ACTA MATERIALIA}, author={Zhang, X and Wang, H and Scattergood, RO and Narayan, J and Koch, CC}, year={2002}, month={Sep}, pages={3995–4004} }
 @article{zhang_wang_kassem_narayan_koch_2002, title={Preparation of bulk ultrafine-grained and nanostructured Zn, Al and their alloys by in situ consolidation of powders during mechanical attrition}, volume={46}, ISSN={["1359-6462"]}, DOI={10.1016/S1359-6462(02)00048-9}, abstractNote={Bulk ultrafine-grained (UFG) or nanostructured Zn, Al and their alloys were produced via in situ consolidation of powders by mechanical attrition (MA) at room temperature. In situ consolidation of metal powders during MA may be a promising method to produce bulk UFG or nanostructured materials with full density and less contamination.}, number={9}, journal={SCRIPTA MATERIALIA}, author={Zhang, X and Wang, H and Kassem, M and Narayan, J and Koch, CC}, year={2002}, month={May}, pages={661–665} }
 @article{saber_koch_fedkiw_2003, title={Pulse current electrodeposition of nanocrystalline zinc}, volume={341}, DOI={10.1016/s0921-5093(02)00198-3}, abstractNote={Pulse electrodeposition exhibits marked advantages over direct current electrodeposition in the control of deposit grain size, surface morphology, and preferred orientation. The effect of pulse peak current density (Jp) on the grain size and surface morphology of zinc deposits with additives (polyacrylamide and thiourea) was studied by scanning electron microscopy and field emission scanning electron microscopy. The preferred orientation of zinc deposits was studied by X-ray diffraction, and microhardness of the deposits was measured by a Knoop microhardness tester. Increasing JP dramatically changed the surface morphology and decreased the grain size. Nanocrystalline zinc (56 nm) was produced at JP=2 A cm−2. At JP equal to 0.4 A cm−2, the preferred orientation of zinc deposits was (112̄2) and changed to the prismatic (112̄0) orientation at Jp equal to 0.8, 1.2, and 1.6 A cm−2. However, increasing the peak current density to 2 A cm−2 altered the prismatic (112̄0) to the random (101̄1). The microhardness increased to approximately 8 times higher than that of pure polycrystalline zinc (0.29 GPa). Microhardness reached a maximum (2.3 GPa) at 1.6 A cm−2, then decreased to 1.5 GPa at 2 A cm−2. The hardness drop was correlated with the presence of additives and the change in texture from (112̄0) to the random (101̄1) with increasing Jp.}, number={1-2}, journal={Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing}, author={Saber, K. and Koch, C. C. and Fedkiw, Peter}, year={2003}, pages={174–181} }
 @article{zhang_wang_scattergood_narayan_koch_sergueeva_mukherjee_2002, title={Studies of deformation mechanisms in ultra-fine-grained and nanostructured Zn}, volume={50}, ISSN={["1359-6454"]}, DOI={10.1016/S1359-6454(02)00349-X}, abstractNote={The temperature, strain rate, grain size and grain size distribution effects on plastic deformation in ultra-fine-grained (UFG) and nanocrystalline Zn are systematically studied. The decrease of ductility with the decrease of average grain size could be an inherent effect in nanocrystalline materials, that is, not determined by processing artifacts. The superior ductility observed in UFG Zn may originate from both dislocation creep within large grains and grain boundary sliding of small nanograins. The stress exponent for dislocation creep is about 6.6. The activation energy for plastic deformation in UFG Zn is close to the activation energy for grain boundary self diffusion in pure Zn.}, number={19}, journal={ACTA MATERIALIA}, author={Zhang, X and Wang, H and Scattergood, RO and Narayan, J and Koch, CC and Sergueeva, AV and Mukherjee, AK}, year={2002}, month={Nov}, pages={4823–4830} }
 @article{zhang_wang_scattergood_narayan_koch_sergueeva_mukherjee_2002, title={Tensile elongation (110%) observed in ultrafine-grained Zn at room temperature}, volume={81}, ISSN={["0003-6951"]}, DOI={10.1063/1.1494866}, abstractNote={Tensile tests were performed for Zn at room temperature, which show elongations of 110%–20% for average grain sizes of 240–23 nm, respectively. The ductility of ultrafine-grained and nanocrystalline Zn was found to decrease with grain size refinement. The deformation mechanisms in ultrafine-grained Zn are believed to be a mixture of grain boundary sliding of small nanograins and intra-grain dislocation creep within the large grains.}, number={5}, journal={APPLIED PHYSICS LETTERS}, author={Zhang, X and Wang, H and Scattergood, RO and Narayan, J and Koch, CC and Sergueeva, AV and Mukherjee, AK}, year={2002}, month={Jul}, pages={823–825} }
 @article{smith_ade_smith_koch_spontak_2001, title={Anomalous phase inversion in polymer blends prepared by cryogenic mechanical alloying}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma001151p}, abstractNote={offer alternative strategies for producing highly dis-persed multicomponent polymer blends. By their verynature, these processes yield fine powders, which mustbe subsequently consolidated or melt-processed to formobjects. While nanoscale dispersion of one polymerwithin the matrix of another has been achieved withoutcompatibilizing agents in binary blends produced byCMA,}, number={6}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Smith, SD and Koch, CC and Spontak, RJ}, year={2001}, month={Mar}, pages={1536–1538} }
 @article{smith_ade_koch_spontak_2001, title={Cryogenic mechanical alloying as an alternative strategy for the recycling of tires}, volume={42}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(00)00804-1}, abstractNote={Cryogenic mechanical alloying (CMA) is investigated as a viable strategy by which to produce highly dispersed blends composed of thermoplastics and tire, thereby providing a potentially new route by which to recycle discarded tires. Morphological characterization of these blends by near-edge X-ray absorption fine structure (NEXAFS) microscopy demonstrates that, upon CMA, ground tire is highly dispersed within poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET) matrices at sub-micron size scales. Incorpo-ration of polyisoprene (PI) homopolymer into the blends to improve dispersion efficacy is also examined. Neither PI nor the tire is found to interact chemically with PMMA or PET under the milling conditions employed here.}, number={9}, journal={POLYMER}, author={Smith, AP and Ade, H and Koch, CC and Spontak, RJ}, year={2001}, month={Apr}, pages={4453–4457} }
 @article{zhang_wang_narayan_koch_2001, title={Evidence for the formation mechanism of nanoscale microstructures in cryomilled Zn powder}, volume={49}, ISSN={["1873-2453"]}, DOI={10.1016/S1359-6454(01)00051-9}, abstractNote={Nanocrystalline Zn powder has been synthesized by a cryomilling method. The average grain size decreased exponentially with the cryomilling time and reached a minimum average grain size of around 17 nm. Large numbers of small grains (2∼6 nm) have been found in the very early stages of cryomilling. Dynamic recrystallization was used to explain the observed phenomena. The exothermic peaks revealed in the differential scanning calorimetry (DSC) results were correlated with the release of microstrain as confirmed by the x-ray diffraction measurements.}, number={8}, journal={ACTA MATERIALIA}, author={Zhang, X and Wang, H and Narayan, J and Koch, CC}, year={2001}, month={May}, pages={1319–1326} }
 @article{wang_sharma_kvit_wei_zhang_koch_narayan_2001, title={Mechanical properties of nanocrystalline and epitaxial TiN films on (100) silicon}, volume={16}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2001.0373}, abstractNote={We investigated mechanical properties of TiN as a function of microstructure varying from nanocrystalline to single crystal TiN films deposited on (100) silicon substrates. By varying the substrate temperature from 25 to 700 °C during pulsed laser deposition, the microstructure of TiN films changed from nanocrystalline (having a uniform grain size of 8 nm) to a single crystal epitaxial film on the silicon (100) substrate. The microstructure and epitaxial nature of these films were investigated using x-ray diffraction and high-resolution transmission electron microscopy. Hardness measurements were made using nanoindentation techniques. The nanocrystalline TiN contained numerous triple junctions without any presence of amorphous regions. The width of the grain boundary remained constant at less than 1 nm as a function of boundary angle. Similarly the grain boundary structure did not change with grain size. The hardness of TiN films decreased with decreasing grain size. This behavior was modeled recently involving grain boundary sliding, which is particularly relevant in the case of hard materials such as TiN.}, number={9}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Wang, H and Sharma, A and Kvit, A and Wei, Q and Zhang, X and Koch, CC and Narayan, J}, year={2001}, month={Sep}, pages={2733–2738} }
 @article{zhang_wang_kassem_narayan_koch_2001, title={Origins of stored enthalpy in cryomilled nanocrystalline Zn}, volume={16}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.2001.0479}, abstractNote={Nanocrystalline Zn was prepared by cryomilling (mechanical attrition at liquid nitrogen temperature). Differential scanning calorimetry (DSC), x-ray diffraction, and transmission electron microscopy were used to study the structural changes and grain size distribution with milling time and subsequent annealing. Maxima in both stored enthalpy (for the low-temperature DSC peak) and lattice strain on the Zn basal planes were observed at the same milling time. Dislocation density on the basal planes is proposed as a major source for lattice strain and the measured stored enthalpy. The released enthalpy that might be due to grain growth is very small.}, number={12}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Zhang, XH and Wang, HY and Kassem, M and Narayan, J and Koch, CC}, year={2001}, month={Dec}, pages={3485–3495} }
 @article{smith_ade_koch_smith_spontak_2000, title={Addition of a block copolymer to polymer blends produced by cryogenic mechanical alloying}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma9915475}, abstractNote={Cryogenic mechanical alloying is used to incorporate a poly(methyl methacrylate-b-isoprene) (MI) diblock copolymer into blends of poly(methyl methacrylate) (PMMA) and polyisoprene (PI). Mechanical milling of the copolymer promotes a reduction in the molar mass of the M block, as discerned from glass transition temperature measurements performed by thermal calorimetry, and induces chemical cross- linking of the I block, as determined from sol-gel analysis. These effects become more pronounced with increasing milling time. Morphological characterization of PMMA-rich PI/MI/PMMA blends by X-ray and electron microscopies reveals that the characteristic size scale of the minority phase decreases with increasing MI content, as well as milling time. The nanostructural features observed in such blends are retained at relatively high MI concentrations during subsequent melt-pressing. Impact testing demon- strates that the blends become tougher upon addition of the MI copolymer, even at relatively low copolymer concentrations. Blend toughness likewise increases with increasing milling time up to a point, beyond which phase inversion occurs within the ternary blends (the PI becomes continuous) and impact strength sharply decreases.}, number={4}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Koch, CC and Smith, SD and Spontak, RJ}, year={2000}, month={Feb}, pages={1163–1172} }
 @article{smith_ade_balik_koch_smith_spontak_2000, title={Cryogenic mechanical alloying of poly(methyl methacrylate) with polyisoprene and poly(ethylene-alt-propylene)}, volume={33}, ISSN={["1520-5835"]}, DOI={10.1021/ma991453v}, abstractNote={Mechanical alloying is performed at cryogenic temperatures to incorporate polyisoprene (PI) or its hydrogenated analogue poly(ethylene-alt-propylene) (PEP) into poly(methyl methacrylate) (PMMA) as an example of high-energy solid-state blending. Morphological characterization of the blends by X-ray and electron microscopies confirms that the degree of dispersion of the constituent polymers improves with increasing milling time. Such dispersion in the PEP/PMMA blends is, however, ultimately compromised by phase coarsening when the materials are postprocessed above the PMMA glass transition temperature in the melt. Milling-induced PI cross-linking serves to suppress phase coarsening in PI/ PMMA blends, which remain relatively well-dispersed even after postprocessing. These blends are generally less fracture-resistant than the as-received PMMA due mainly to the accompanying reduction in PMMA molecular weight. Their optical transparency is observed to decrease dramatically with increasing PEP or PI concentration until they appear opaque. An overall improvement in blend properties by mechanical alloying is, however, anticipated upon judicious selection of more degradation-resistant polymers.}, number={7}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Balik, CM and Koch, CC and Smith, SD and Spontak, RJ}, year={2000}, month={Apr}, pages={2595–2604} }
 @article{koch_2000, title={Experimental evidence for magnetic or electric field effects on phase transformations}, volume={287}, ISSN={["1873-4936"]}, DOI={10.1016/s0921-5093(00)00778-4}, abstractNote={This review presents examples of the effects of magnetic or electric fields on phase transformations in a variety of materials. Magnetic fields have been shown to influence phase stability and, for example, induce martensite in iron–base alloys. Application of a magnetic field during the growth of some phases can produce an alignment with the field and an optimized microstructure for certain properties. Electric fields can modify phase transformations by their enhancement of atomic diffusivity, as, for example, their influence on diffusion-controlled transformations such as eutectoidal decomposition of steel or age hardening of aluminum alloys. Electric fields can also bias phase transformations toward phases which have higher dielectric constants than the parent phase. Much more research is needed to fully exploit magnetic/electric fields as another tool to control structure, and therefore properties of materials.}, number={2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Koch, CC}, year={2000}, month={Aug}, pages={213–218} }
 @article{smith_shay_spontak_balik_ade_smith_koch_2000, title={High-energy mechanical milling of poly(methyl methacrylate), polyisoprene and poly(ethylene-alt-propylene)}, volume={41}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(99)00830-7}, abstractNote={High-energy mechanical milling has been performed on poly(methyl methacrylate) (PMMA) at ambient and cryogenic temperatures, as well as on polyisoprene (PI) and poly(ethylene-alt-propylene) (PEP) at cryogenic conditions only. Milling conducted at ambient temperature has a substantially greater impact on the molecular characteristics of PMMA than milling at cryogenic temperatures. An increase in the milling time is accompanied by substantial reductions in PMMA molecular weight and, hence, glass transition temperature and impact strength under both sets of experimental conditions. An unexpected trend identified here is that the PMMA molecular weight distribution initially broadens and subsequently narrows with increasing milling time. Solid-state mechanical milling promotes comparable decreases in molecular weight and glass transition temperature in PEP (at a slower rate relative to PMMA), but induces chemical crosslinking in PI, as confirmed by FTIR spectroscopy. Charlesby–Pinner analysis yields not only the degree of PI crosslinking, but also the relative crosslinking and scission rates of PI, during cryogenic milling.}, number={16}, journal={POLYMER}, author={Smith, AP and Shay, JS and Spontak, RJ and Balik, CM and Ade, H and Smith, SD and Koch, CC}, year={2000}, month={Jul}, pages={6271–6283} }
 @misc{suryanarayana_koch_2000, title={Nanocrystalline materials - Current research and future directions}, volume={130}, ISSN={["1572-9540"]}, DOI={10.1023/A:1011026900989}, number={1-4}, journal={HYPERFINE INTERACTIONS}, author={Suryanarayana, C and Koch, CC}, year={2000}, pages={5–44} }
 @inproceedings{koch_smith_bai_spontak_balik_2000, title={Nonequilibrium processing of polymeric materials by mechanical attrition}, volume={343/346}, number={pts.1&2}, booktitle={International Symposium on Metastable, Mechanically Alloyed and Nanocrystalline Materials (1999: Dresden, Germany)}, publisher={Utikon-Zurich, Switz.; Enfield, NH: Trans Tech Publications}, author={Koch, C. C. and Smith, A. P. and Bai, C. and Spontak, R. J. and Balik, C. M.}, editor={J. Eckert, H. Schlorb and Schultz, L.Editors}, year={2000}, pages={49–561} }
 @article{bai_spontak_koch_saw_balik_2000, title={Structural changes in poly(ethylene terephthalate) induced by mechanical milling}, volume={41}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(00)00048-3}, abstractNote={Poly(ethylene terephthalate) (PET) has been subjected to high-energy ball milling (mechanical milling, MM) at three different temperatures. The resulting milled powder is characterized by molecular weight measurements, differential scanning calorimetry and wide-angle X-ray scattering. Regardless of the initial degree of crystallinity or milling temperature employed, MM apparently yields an "oriented amorphous" PET morphology in which the PET chains are locally aligned but rotationally disordered. This conclusion is based on the persistence of the (100) peak in otherwise amorphous x-ray patterns from milled PET. Thermograms of milled PET exhibit a small, broad crystallization exotherm and a large melting endotherm. The unusually small crystallization enthalpy is attributed to the local orientation of PET molecules present in the oriented amorphous morphology. Only minor rotations and translations of oriented PET molecules are needed to put the chains into register and, hence, the crystalline state. Evidence is also presented to suggest that extended-chain crystals of PET are produced upon crystallization of mechanically milled PET.}, number={19}, journal={POLYMER}, author={Bai, C and Spontak, RJ and Koch, CC and Saw, CK and Balik, CM}, year={2000}, month={Jun}, pages={7147–7157} }
 @article{smith_spontak_koch_smith_ade_2000, title={Temperature-induced morphological evolution in polymer blends produced by cryogenic mechanical alloying}, volume={274}, DOI={10.1002/(sici)1439-2054(20000101)274:1<1::aid-mame1>3.3.co;2-r}, number={1}, journal={Macromolecular Materials and Engineering}, author={Smith, A. P. and Spontak, Richard and Koch, C. C. and Smith, S. D. and Ade, H.}, year={2000}, pages={1–12} }
 @article{smith_spontak_ade_smith_koch_1999, title={High-energy cryogenic blending and compatibilizing of immiscible polymers}, volume={11}, ISSN={["1521-4095"]}, DOI={10.1002/(SICI)1521-4095(199910)11:15<1277::AID-ADMA1277>3.0.CO;2-9}, abstractNote={ciency Z in solid films of PA-PPV and MEH-PPV has been determined by xerographic discharge experiments over two orders of magnitude in field and for different illumination wavelengths. Onsager's theory with a Gaussian distribution of electron±hole radii describes the electric field dependences of Z well. The large distribution parameter a is a characteristic of a small electron±hole pair binding energy of approximately 0.1±0.2 eV. For both polymers, high efficiencies of up to 20 % at a field of 100 V/mm were measured. Within the polymer absorption, Z was found to be nearly independent of wavelength. This is in agreement with the well established picture of a fast vibronic and energetic relaxation following photoexcitation. Addition of C60 to PA-PPV increases the primary quantum yield to unity and photogeneration efficiencies of up to 50 % are measured.}, number={15}, journal={ADVANCED MATERIALS}, author={Smith, AP and Spontak, RJ and Ade, H and Smith, SD and Koch, CC}, year={1999}, month={Oct}, pages={1277-+} }
 @article{fahmy_shen_tucker_spontak_koch_1999, title={Possible evidence for the stabilization of beta-carbon nitride by high-energy ball milling}, volume={14}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.1999.0334}, abstractNote={The possibility of stabilizing the theoretically predicted β–C3N4phase by high-energy ball milling is investigated. Charges of graphitic carbon were milled with and without minor alloying additions under different atmospheric media, namely gas and/or liquid phases of nitrogen, air, or ammonia. Milling was performed at either of two energy levels for periods of up to 48 h. The β–C3N4phase was found to exist as small crystallites in a matrix of primarily amorphous carbon at volume fractions estimated between 5 and 10 at.%. High-resolution electron diffraction and x-ray diffraction indicate that the crystalline nature of the C3N4phase corresponds with a hexagonal lattice witha= 6.46 Å andc/a= 0.374, which are within 2% of the theoretically calculated lattice parameter values. Analysis of electron energy-loss spectroscopy (EELS), x-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectra verify the presence of chemically bonded carbon and nitrogen with chemical states reflecting combinedsp2andsp3hybridization. Chemical analysis confirms nitrogen enrichment at levels consistent with the C3N4stoichiometry and the estimated degree of stabilization. The possible mechanism(s) responsible for the stabilization of the β–C3N4phase are briefly discussed.}, number={6}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Fahmy, Y and Shen, TD and Tucker, DA and Spontak, RL and Koch, CC}, year={1999}, month={Jun}, pages={2488–2499} }
 @article{malow_koch_miraglia_murty_1998, title={Compressive mechanical behavior of nanocrystalline Fe investigated with an automated ball indentation technique}, volume={252}, ISSN={["0921-5093"]}, DOI={10.1016/s0921-5093(98)00661-3}, abstractNote={Nanocrystalline (nc) iron was produced by mechanical attrition and compacted into near fully dense samples. Isothermal annealing at 800 K resulted in grain sizes between 15 and 24 nm. A newly available Automated Ball Indentation system was used to study the compressive mechanical properties of the samples. The ABI method proved useful in examining the mechanical properties of nc iron on a more quantitative level than previously possible by conventional hardness testing methods. Stress–strain curves were obtained which indicated a compressive behavior similar to that of perfectly plastic materials: low strain hardening at high flow stresses around 3 GPa and a low room-temperature strain-rate sensitivity. The flow stresses were independent of the grain size in the range of the present study. The deformation pile-up around the indentations seems to have formed inhomogeneously, exhibiting intense plastic deformation in localized shear bands.}, number={1}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Malow, TR and Koch, CC and Miraglia, PQ and Murty, KL}, year={1998}, month={Aug}, pages={36–43} }
 @article{koch_1998, title={Intermetallic matrix composites prepared by mechanical alloying - a review}, volume={244}, ISSN={["0921-5093"]}, DOI={10.1016/s0921-5093(97)00824-1}, abstractNote={This paper reviews research on intermetallic matrix composites synthesized by mechanical alloying. Mechanical alloying, as a powder processing method, results in discontinuous second phases, i.e. dispersoids/discontinuous reinforcements, in the intermetallic matrix. After a discussion of earlier work on dispersoids in intermetallics, intermetallic matrix composites prepared by mechanical alloying will be reviewed for the important structural intermetallics Fe–40 at.% Al, NiAl, Ni3Al, and MoSi2. The unique microstructure and properties of intermetallic matrix dispersoid systems produced by cryomilling will be discussed. The limited studies of nanocrystalline intermetallic matrix composites suggest the possibility of superplastic forming of these materials.}, number={1}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Koch, CC}, year={1998}, month={Mar}, pages={39–48} }
 @article{saleh_schindler_sarma_haase_koch_kingon_1998, title={Isolation techniques and electrical characterization of single grain boundaries of Bi2Sr2CaCu2O2 high-temperature superconductor}, volume={295}, ISSN={["0921-4534"]}, DOI={10.1016/s0921-4534(97)01762-0}, abstractNote={We have isolated single grain boundaries of a bulk material of polycrystalline high-temperature superconductor Bi2Sr2CaCu2O2 (Bi-2212) tapes. The tapes were grown on a single crystal of MgO or Ag-foil by partial melting of the superconductor. The isolation techniques consisted of fabricating metal micro-contact pads, wire bonding, and laser patterning of the Bi-2212 superconductor. Results of electrical and magnetic measurements of single grain boundaries suggested a possible existence of Josephson-like junctions coexisting with flux flow junctions. In contrast to bulk samples, Tc of a single grain boundary did not change by applying magnetic field. Jc and Tc were found to be greatly dependent on heat treatment and growth conditions. The current–voltage characteristics of a single patterned bridge followed a relation of the form V∼(I−Ic)n for I>Ic with n∼1.2.}, number={3-4}, journal={PHYSICA C}, author={Saleh, AM and Schindler, G and Sarma, C and Haase, DG and Koch, CC and Kingon, AI}, year={1998}, month={Feb}, pages={225–234} }
 @article{malow_koch_1998, title={Mechanical properties in tension of mechanically attrited nanocrystalline iron by the use of the miniaturized disk bend test}, volume={46}, ISSN={["1359-6454"]}, DOI={10.1016/S1359-6454(98)00294-8}, abstractNote={The mechanical properties of warm compacted nanocrystalline (nc) iron powder compacts of near theoretical density in the grain size range between 8 and 33 nm were investigated. The elastic and plastic behavior were characterized by miniaturized disk bend tests and hardness measurements. Light and scanning electron microscopy (SEM) were used to document the deformation and fracture morphologies. The Young's modulus of the nc Fe was essentially the same as that of coarse grained Fe. All samples failed in a macroscopically brittle manner. Local plasticity in shear bands was observed in the samples with the larger grain sizes (>20 nm). An increasing failure stress with increasing grain size is probably due to a processing effect on the flaw controlled failure of the samples. The results are discussed in the context of the deformation and fracture behavior of micrometer grain size metals and alloys.}, number={18}, journal={ACTA MATERIALIA}, author={Malow, TR and Koch, CC}, year={1998}, month={Nov}, pages={6459–6473} }
 @article{malow_koch_1998, title={Mechanical properties, ductility, and grain size of nanocrystalline iron produced by mechanical attrition}, volume={29}, ISSN={["1073-5623"]}, DOI={10.1007/s11661-998-0106-1}, number={9}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Malow, TR and Koch, CC}, year={1998}, month={Sep}, pages={2285–2295} }
 @article{smith_bai_ade_spontak_balik_koch_1998, title={X-ray microscopy characterization of a thermoplastic / liquid crystalline polymer blend produced by mechanical alloying}, volume={19}, DOI={10.1002/marc.1998.030191104}, abstractNote={Incorporation of liquid crystalline polymers (LCPs) into commodity polymers remains a challenge in the design of high-performance, low-cost polymeric blends. Blends of a thermoplastic polymer and a nematic LCP are produced here by mechanical alloying. Functionality sensitive X-ray microscopy reveals LCP dispersions as small as 100 nm in diameter. Intimate mixing remains upon subsequent melt processing, indicating that mechanical alloying is suited for applications such as recycling.}, number={1998}, journal={Macromolecular Rapid Communications}, author={Smith, Andy and Bai, C. and Ade, H. and Spontak, Richard and Balik, C. M. and Koch, C. C.}, year={1998}, pages={557} }
 @article{malow_koch_1997, title={Grain growth in nanocrystalline iron prepared by mechanical attrition}, volume={45}, ISSN={["1359-6454"]}, DOI={10.1016/S1359-6454(96)00300-X}, abstractNote={The grain growth in nanocrystalline Fe produced by high energy ball milling is investigated. Grain growth data are analysed using two different models of grain growth, one of which takes pinning forces on the grain boundaries into account. The grain growth exponents nD1n − D1no = kt for nanocrystalline and conventional polycrystalline Fe are compared. The use of the above mentioned equation yields an activation energy of 125 kJ/mol, while the second model gives 248 kJ/mol. These values are compared to those for grain boundary and lattice diffusion in Fe. Some evidence for two different sets of mechanisms governing the grain growth in nanocrystalline Fe are discussed.}, number={5}, journal={ACTA MATERIALIA}, author={Malow, TR and Koch, CC}, year={1997}, month={May}, pages={2177–2186} }
 @inproceedings{balik_bai_koch_spontak_saw_1997, title={Mechanical alloying of PET and PET/Vectra blends}, volume={461}, booktitle={Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings)}, publisher={Warrendale, PA: Materials Research Society}, author={Balik, C. M. and Bai, C. and Koch, C. C. and Spontak, R. J. and Saw, C. K.}, editor={R. M. Briber, C. C. Han and Peiffer, D. G.Editors}, year={1997}, pages={39} }
 @article{shen_shmagin_koch_kolbas_fahmy_bergman_nemanich_mcclure_sitar_quan_1997, title={Photoluminescence from mechanically milled Si and SiO2 powders}, volume={55}, ISSN={["0163-1829"]}, DOI={10.1103/physrevb.55.7615}, abstractNote={The photoluminescence (PL) in as-received and milled Si and SiO2 powder is reported. The Si and SiO2 powder is characterized by chemical analysis, Raman scattering, x-ray photoelectron spectra, infrared absorption, x-ray diffraction, and differential thermal analysis. The results indicate that the Si powder has amorphous Si oxide and suboxide surface layers. The milling of Si powder results in the formation of nanocrystalline/amorphous Si components. An amorphous SiO2 component is formed by milling crystalline SiO2. The PL spectra for as-received Si, milled Si, and SiO2 powder exhibit similar peak shapes, peak maxima, and full width at half maximum values. For both the as-received and the milled Si powder, experimental results appear to exclude mechanisms for PL related to an amorphous Si component or Si-H or Si-OH bonds, or the quantum confinement effect. Similarly, for milled SiO2 powder mechanisms for PL do not appear related to Si-H or Si-OH bonds. Instead the greatly increased intensity of PL for milled SiO2 can be related to both the increased volume fraction of the amorphous SiO2 component and the increased density of defects introduced in the amorphous SiO2 upon milling. It is suggested that the PL for as-received Si, milling-induced nanocrystalline/amorphous Si, and milled SiO2 results from defects, such as the nonbridging oxygen hole center, in the amorphous Si suboxide and/or SiO2 components existing in these powder samples. The PL measurement for milled SiO2 is dependent on air pressure whereas that for as-received SiO2 is not, suggesting that new emitting centers are formed by milling.}, number={12}, journal={PHYSICAL REVIEW B}, author={Shen, TD and Shmagin, I and Koch, CC and Kolbas, RM and Fahmy, Y and Bergman, L and Nemanich, RJ and McClure, MT and Sitar, Z and Quan, MX}, year={1997}, month={Mar}, pages={7615–7623} }
 @article{shen_koch_wang_quan_wang_1997, title={Solid-state reaction in nanocrystalline Fe/SiC composites prepared by mechanical alloying}, volume={32}, ISSN={["0022-2461"]}, DOI={10.1023/A:1018688009913}, number={14}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Shen, TD and Koch, CC and Wang, KY and Quan, MX and Wang, JT}, year={1997}, month={Jul}, pages={3835–3839} }
 @article{koch_1997, title={Synthesis of nanostructured materials by mechanical milling: Problems and opportunities}, volume={9}, ISSN={["0965-9773"]}, DOI={10.1016/S0965-9773(97)00014-7}, abstractNote={Mechanical attrition as a method to produce nanocrystalline (nc) materials is reviewed. Its advantages include the fact that all classes of materials — including brittle compounds — are amenable to the method; it can be easily scaled up to tonnage quantities. The phenomenology and suggested mechanisms for formation of nc microstructures are discussed for ball milling of single component powders, mechanical alloying of multi-component powders, and mechanical crystallization of amorphous alloys. The phenomenology is well documented but microscopic mechanisms await better understanding of the nature of deformation processes in nc materials. The problems of contamination and powder consolidation are briefly considered.}, number={1-8}, journal={NANOSTRUCTURED MATERIALS}, author={Koch, CC}, year={1997}, pages={13–22} }
 @article{leonard_koch_1997, title={X-ray intensity decrease from absorption effects in mechanically milled systems}, volume={36}, ISSN={["1359-6462"]}, DOI={10.1016/S1359-6462(96)00333-8}, abstractNote={Mixing strong and weak x-ray absorbers will result in changes in the diffraction intensity, which can be predicted by the preceding model given by Klug and Alexander. The level of mixing, however, is important: with large powder particles the diffraction reveals the composition of the powder with no anomalous decrease in intensity; with small particle powders intermixed by means such as mechanical milling, the diffraction intensity will change in accordance with the materials' linear absorption. The component with the lower x-ray linear absorption coefficient will exhibit much lower diffraction intensities than a rule of mixtures would predict. Good quantitative agreement between experimental intensities for the SiSn system and those predicted by the Klug and Alexander model was observed.}, number={1}, journal={SCRIPTA MATERIALIA}, author={Leonard, RT and Koch, CC}, year={1997}, month={Jan}, pages={41–46} }
 @article{jang_koch_1990, title={AMORPHIZATION AND DISORDERING OF THE NI3AL ORDERED INTERMETALLIC BY MECHANICAL MILLING}, volume={5}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.1990.0498}, abstractNote={The ordered fcc intermetallic compound Ni3Al was mechanically milled in a high energy ball mill. The severe plastic deformation produced by milling induced transformations with increasing milling time as follows: ordered fcc → 2; disordered fcc → 2; nanocrystalline fcc + amorphous. The milling time for complete disordering occurred at 5 h for stoichiometric Ni3Al milled at ambient temperature compared to 50 h for the first observation of an amorphous structure. The structural and microstructural evolution with milling time was followed by x-ray diffraction, TEM, hardness, and calorimetry. The major defect believed responsible for inducing the crystalline-to-amorphous transformation is the fine grain boundary structure with nanometer (∼2 nm diameter) dimensions. The calculated interfacial free energy of the grain boundaries is consistent with the estimated free energy difference between the fcc and amorphous phases in Ni3Al.}, number={3}, journal={JOURNAL OF MATERIALS RESEARCH}, author={JANG, JSC and KOCH, CC}, year={1990}, month={Mar}, pages={498–510} }
 @misc{koch_1989, title={MATERIALS SYNTHESIS BY MECHANICAL ALLOYING}, volume={19}, ISSN={["0084-6600"]}, DOI={10.1146/annurev.ms.19.080189.001005}, abstractNote={Novel processing methods have received much attention in recent years. This interest is driven by the need to develop new and improved materials to lift material limitations on many applications. Nonequilibrium pro­ cessing methods that result in metastable structures can often synthesize materials with unique properties. Enormous effort has been devoted to one of these techniques, namely, rapid solidification. Rapid solidification methods can modify materials by refining the microstructure, homo­ genizing the composition, extending solid solubilities, creating metastable crystalline phases, or producing metallic glasses. Parallel material modi­ fications can be achieved with the relatively less-studied technique of mechanical alloying (MA). The thesis of this review is that mechanical alloying is a nonequilibrium processing technique analogous to rapid solidification with specific advantages and disadvantages. Mechanical alloying was first developed by Benjamin and coworkers at the International Nickel Company in the late 1960s (1). The goal of this effort was the production of complex oxide dispersion-strengthened (ODS) alloys. The commercial applications of MA have centered on the devel­ opment of ODS Ni-base superalloys, Fe-base ODS alloys, ODS aluminum alloys, and coatings for high temperature alloys. Several reviews of MA have appeared in recent years in which the development of the ODS alloys has been covered (2, 3, 4, 5). This subject will therefore not be considered in detail in the review. The synthesis of amorphous alloys by MA has been reviewed recently by Weeber and Bakker (6). However, since this is a relatively recent area of research and not as well-known as the ODS work, a summary of the main results will be included in the review.}, journal={ANNUAL REVIEW OF MATERIALS SCIENCE}, author={KOCH, CC}, year={1989}, pages={121–143} }
 @article{schwarz_koch_1986, title={FORMATION OF AMORPHOUS-ALLOYS BY THE MECHANICAL ALLOYING OF CRYSTALLINE POWDERS OF PURE METALS AND POWDERS OF INTERMETALLICS}, volume={49}, ISSN={["0003-6951"]}, DOI={10.1063/1.97206}, abstractNote={Amorphous powders of Ni32Ti68 and of Ni45Nb55 were synthesized by mechanical alloying (MA) starting from either a mixture of pure metal powders (in the appropriate molar ratio) or from powders of the crystalline intermetallics NiTi2 and Ni45Nb55, respectively. For both alloys, the peak temperature increase (above the average processing temperature) in the powder particles trapped between colliding balls is estimated at 38 K. Thus, the amorphization is attributed to a process other than the formation of local melts followed by the rapid solidification of these melts into the amorphous phase. The amorphization by MA starting from a mixture of pure crystalline powders is attributed to a solid state interdiffusion reaction, the kinetics of which is controlled by the excess point and lattice defects generated by plastic deformation. The amorphization by MA starting from powders of crystalline intermetallics is attributed to the accumulation of point and lattice defects which raise the free energy of the faulted intermetallic above that of the amorphous alloy.}, number={3}, journal={APPLIED PHYSICS LETTERS}, author={SCHWARZ, RB and KOCH, CC}, year={1986}, month={Jul}, pages={146–148} }
 @article{gupta_raman_koch_murty, title={Effect of nanocrystalline structure on the corrosion of a Fe20Cr alloy}, volume={8}, number={5}, journal={International Journal of Electrochemical Science}, author={Gupta, R. K. and Raman, R. K. S. and Koch, C. C. and Murty, B. S.}, pages={6791–6806} }
 @article{zhang_wang_koch, title={Mechanical behavior of bulk ultrafine-grained and nanocrystalline Zn}, volume={6}, number={2}, journal={Reviews on Advanced Materials Science}, author={Zhang, X. and Wang, H. and Koch, C. C.}, pages={53–93} }
 @book{nanostructured materials: processing, properties, and applications. (2nd ed.), ISBN={0815515340}, publisher={Norwich, NY: William Andrew Pub.} }
 @book{nanostructured materials: processing, properties, and potential applications, ISBN={0815514514}, publisher={Norwich, NY: Noyes Publications/ William Andrew Publishing} }
 @book{koch_al., title={Structural nanocrystalline materials: Fundamentals and applications}, ISBN={0521855659}, publisher={Cambridge; New York: Cambridge University Press}, author={Koch, C. C. and al.} }
 @misc{gupta_darling_raman_ravi_koch_murty_scattergood, title={Synthesis, characterization and mechanical behaviour of an in situ consolidated nanocrystalline FeCrNi alloy}, volume={47}, number={3}, journal={Journal of Materials Science}, author={Gupta, R. K. and Darling, K. S. and Raman, R. K. S. and Ravi, K. R. and Koch, C. C. and Murty, B. S. and Scattergood, R. O.}, pages={1562–1566} }
 @inproceedings{koch_scattergood_kotan_saber, title={Thermal stability of nanocrystalline grain size in ternary FE-base alloys}, volume={753}, booktitle={Recrystallization and grain growth v}, author={Koch, C. C. and Scattergood, R. O. and Kotan, H. and Saber, M.}, pages={341–344} }
 @inproceedings{koch_scattergood_vanleeuwen_darling, title={Thermodynamic stabilization of grain size in nanocrystalline metals}, volume={715-716}, booktitle={Recrystallization and grain growth iv}, author={Koch, C. C. and Scattergood, R. O. and VanLeeuwen, B. K. and Darling, K. A.}, pages={323–328} }