@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{wang_huang_li_guo_he_wang_wu_scattergood_zhu_2020, title={Dense dispersed shear bands in gradient-structured Ni}, volume={124}, ISSN={["1879-2154"]}, DOI={10.1016/j.ijplas.2019.08.012}, abstractNote={During tensile deformation, nanostructured (NS) metals often fail soon after yielding by forming a localized shear band. Here we report the observation of high density of shear bands that are homogeneously dispersed in the NS layer of a gradient Ni sample. These shear bands were nucleated at early elastic/plastic strain stage, reached number saturation at ∼3% strain, and remained arrested by the central coarse-grained (CG) matrix during the entire plastic deformation, resulting in a uniform tensile plasticity comparable to that of CG matrix. The formation of dispersed shear bands was promoted by the elastic/plastic interaction between NS surface layer and CG matrix, and affected by the surface roughness and the hardness variation in the NS surface layer. The width of shear bands remained constant, but the intensity of strain accumulation increased almost linearly with applied tensile strain, suggesting a stable shear banding process. Microstructure examination revealed that the strain in shear bands was accommodated by mechanically driven grain boundary migration and grain coarsening. These results clarify the fundamental questions: why/how does the NS layer supported by CG matrix achieve large uniform elongation? Moreover, the findings demonstrate the possibility of activating dispersed stable shear bands by synthesizing gradient architecture for optimized mechanical performances, i.e., a new strategy for evading the strength-ductility tradeoff in NS metals.}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Wang, Yanfei and Huang, Chongxiang and Li, Yusheng and Guo, Fengjiao and He, Qiong and Wang, Mingsai and Wu, Xiaolei and Scattergood, Ronald O. and Zhu, Yuntian}, year={2020}, month={Jan}, pages={186–198} }
 @article{wang_wang_fang_guo_liu_scattergood_huang_zhu_2019, title={Extra strengthening in a coarse/ultrafine grained laminate: Role of gradient interfaces}, volume={123}, ISSN={["1879-2154"]}, DOI={10.1016/j.ijplas.2019.07.019}, abstractNote={The interfaces introduced in metals by heterostructural design play crucial roles in mechanical behaviors. Here the effect of gradient interfaces on mechanical behavior was investigated in a laminated Cu–30Zn sample composed of coarse-grained and ultrafine-grained layers. Tensile tests revealed a superior strength-ductility synergy with extraordinary strengthening and work hardening. By combining the measurements of height contour and strain distribution using digital image correlation, the development of strain gradient was detected in the near-interface zone during tension, which was caused by the mechanical incompatibilities across interfaces and the synergetic constraint between layers. The intensity of strain gradient in the near-interface zone increased with tensile strain, which was accommodated by the accumulation of geometrically necessary dislocations, thereby resulting in extra back stress and dislocation strengthening.}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Wang, Y. F. and Wang, M. S. and Fang, X. T. and Guo, F. J. and Liu, H. Q. and Scattergood, R. O. and Huang, C. X. and Zhu, Y. T.}, year={2019}, month={Dec}, pages={196–207} }
 @article{abaza_al-sulaiti_scattergood_youssef_2019, title={Influence of 1%Nb Solute Addition on the Thermal Stability of In Situ Consolidated Nanocrystalline Cu}, volume={21}, ISSN={["1527-2648"]}, DOI={10.1002/adem.201800859}, abstractNote={Nanocrystalline (nc) Cu and Cu–1% Nb bulk materials are synthesized using a combination of cryogenic and room temperature ball milling. The grain size values of these in situ consolidated Cu and Cu–1% Nb, determined using transmission electron microscopy, are found to be 22 nm and 18 nm, respectively. In this investigation, isochronal heat treatments are performed for 1 h to establish grain size and microstructural changes as a function of temperature. The annealing of nc Cu–1% Nb at a temperature of 1073 K reveals a slight increase in the average grain size from 18 to 45 nm. The grain size of nc Cu, however, increases from 22 nm to about 3 μm after annealing at the same conditions. The present results indicate that solute entrapment plays a major role in thermal stability of the high purity contaminant‐free Cu with the addition of only 1 at% Nb after annealing for 1 h up to a homologous temperature of 0.8. Kinetic stabilization via clustering of Nb atoms on the grain boundaries and the triple junctions is also observed after annealing at high temperature for longer times.}, number={4}, journal={ADVANCED ENGINEERING MATERIALS}, author={Abaza, Mohamed A. and Al-Sulaiti, Leena and Scattergood, Ronald O. and Youssef, Khaled M.}, year={2019}, month={Apr} }
 @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} }
 @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{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{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{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{shahbeigi roodposhti_sarkar_murty_scattergood_2016, title={Effects of Microstructure and Processing Methods on Creep Behavior of AZ91 Magnesium Alloy}, volume={25}, ISSN={1059-9495 1544-1024}, url={http://dx.doi.org/10.1007/S11665-016-2222-1}, DOI={10.1007/S11665-016-2222-1}, number={9}, journal={Journal of Materials Engineering and Performance}, publisher={Springer Science and Business Media LLC}, author={Shahbeigi Roodposhti, Peiman and Sarkar, Apu and Murty, Korukonda L. and Scattergood, Ronald O.}, year={2016}, month={Jul}, pages={3697–3709} }
 @article{roodposhti_sarkar_murty_brody_scattergood_2016, title={Grain boundary sliding mechanism during high temperature deformation of AZ31 Magnesium alloy}, volume={669}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2016.05.076}, abstractNote={High temperature tensile creep tests were conducted on AZ31 Magnesium alloy at low stress range of 1–13 MPa to clarify the existence of grain boundary sliding (GBS) mechanism during creep deformation. Experimental data within the GBS regime shows the stress exponent is ~2 and the activation energy value is close to that for grain boundary diffusion. Analyses of the fracture surface of the sample revealed that the GBS provides many stress concentrated sites for diffusional cavities formation and leads to premature failure. Scanning electron microscopy images show the appearances of both ductile and brittle type fracture mechanism. X-ray diffraction line profile analysis (based on Williamson-Hall technique) shows a reduction in dislocation density due to dynamic recovery (DRV). A correlation between experimental data and Langdon's model for GBS was also demonstrated.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Roodposhti, Peiman Shahbeigi and Sarkar, Apu and Murty, Korukonda Linga and Brody, Harold and Scattergood, Ronald}, year={2016}, month={Jul}, pages={171–177} }
 @article{roodposhti_sarkar_murty_scattergood_2015, title={Dislocation Density Evolution During Creep of AZ31 Mg Alloy: A Study by X-ray Diffraction Line Profile Analysis}, volume={4}, ISSN={2192-9262 2192-9270}, url={http://dx.doi.org/10.1007/S13632-015-0220-6}, DOI={10.1007/S13632-015-0220-6}, number={5}, journal={Metallography, Microstructure, and Analysis}, publisher={Springer Science and Business Media LLC}, author={Roodposhti, Peiman Shahbeigi and Sarkar, Apu and Murty, Korukonda L. and Scattergood, Ronald O.}, year={2015}, month={Sep}, pages={337–343} }
 @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{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{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{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{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{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{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{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{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{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{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{chan_stoner_thompson_scattergood_piascik_2013, title={Fracture toughness improvements of dental ceramic through use of yttria-stabilized zirconia (YSZ) thin-film coatings}, volume={29}, ISSN={["1879-0097"]}, DOI={10.1016/j.dental.2013.05.003}, abstractNote={The aim of this study was to evaluate strengthening mechanisms of yttria-stabilized zirconia (YSZ) thin film coatings as a viable method for improving fracture toughness of all-ceramic dental restorations.Bars (2mm×2mm×15mm, n=12) were cut from porcelain (ProCAD, Ivoclar-Vivadent) blocks and wet-polished through 1200-grit using SiC abrasive. A Vickers indenter was used to induce flaws with controlled size and geometry. Depositions were performed via radio frequency magnetron sputtering (5mT, 25°C, 30:1 Ar/O2 gas ratio) with varying powers of substrate bias. Film and flaw properties were characterized by optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Flexural strength was determined by three-point bending. Fracture toughness values were calculated from flaw size and fracture strength.Data show improvements in fracture strength of up to 57% over unmodified specimens. XRD analysis shows that films deposited with higher substrate bias displayed a high %monoclinic volume fraction (19%) compared to non-biased deposited films (87%), and resulted in increased film stresses and modified YSZ microstructures. SEM analysis shows critical flaw sizes of 67±1μm leading to fracture toughness improvements of 55% over unmodified specimens.Data support surface modification of dental ceramics with YSZ thin film coatings to improve fracture toughness. Increase in construct strength was attributed to increase in compressive film stresses and modified YSZ thin film microstructures. It is believed that this surface modification may lead to significant improvements and overall reliability of all-ceramic dental restorations.}, number={8}, journal={DENTAL MATERIALS}, author={Chan, Ryan N. and Stoner, Brian R. and Thompson, Jeffrey Y. and Scattergood, Ronald O. and Piascik, Jeffrey R.}, year={2013}, month={Aug}, pages={881–887} }
 @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{zdanowicz_dow_scattergood_youssef_2013, title={Nanostructure fabrication on germanium and silicon by nanocoining imprint technique}, volume={37}, ISSN={["1873-2372"]}, DOI={10.1016/j.precisioneng.2013.05.004}, abstractNote={Germanium (Ge) and silicon (Si) material response to indentation with a nanostructured die is investigated. A diamond die attached to a high speed actuator previously used to create large arrays of nanofeatures on metallic surfaces was used to create nanofeatures on Ge and Si samples. The pressure induced transformation of Ge and Si from a diamond cubic brittle phase to a more ductile beta-tin metallic phase due to the nanofeatures on the die was investigated. Results using the dynamic nanocoining method showed chip-like deformation around the individual nanofeatures indicative of the beta-tin phase transformation at the nanofeature level. Micro-Raman measurements confirmed the metallic transition from evidence including metastable and amorphous phases after indentation. Indents created using a common linear indentation method exhibited similar behavior. The Si nanofeature deformation was compared to electroless (EL) nickel and the deformation differed as dictated by the mechanism of material flow. Although not observed in Si, fracture occurred in some Ge indents at higher loads as a result of the lower fracture toughness compared to Si.}, number={4}, journal={PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY}, author={Zdanowicz, Erik and Dow, Thomas A. and Scattergood, Ronald O. and Youssef, Khaled}, year={2013}, month={Oct}, pages={871–879} }
 @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{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{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{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_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_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{lane_dow_scattergood_2013, title={Thermo-chemical wear model and worn tool shapes for single-crystal diamond tools cutting steel}, volume={300}, ISSN={["1873-2577"]}, DOI={10.1016/j.wear.2013.02.012}, abstractNote={An Arrhenius-type thermochemical wear model proposed by past researchers is evaluated for predicting diamond tool wear when machining low carbon steel. Tool temperature values are determined using finite element modeling. These temperatures are related to tool wear measured after diamond turning tests on a low carbon steel workpiece to determine constants in the Arrhenius-type model. Measured tool wear shows a transition in worn tool shape from low speed (1 mm/s) to high speed (4 m/s) machining tests. Model results show a minimum value of wear per cutting distance occurs at a cutting speed of 2.5 m/s. The model also gives an activation energy between 25.0 kJ/mol and 29.3 kJ/mol. In addition, this model is used to explain experimental results obtained by others researching chemical wear of diamond.}, number={1-2}, journal={WEAR}, author={Lane, B. M. and Dow, T. A. and Scattergood, R.}, year={2013}, month={Mar}, pages={216–224} }
 @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{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{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{zdanowicz_dow_scattergood_2012, title={Rapid fabrication of nanostructured surfaces using nanocoining}, volume={23}, ISSN={["0957-4484"]}, DOI={10.1088/0957-4484/23/41/415303}, abstractNote={A new process for creating high quality ordered arrays of nanofeatures called nanocoining is presented. A diamond die with a structured area of nanofeatures (1600 features in a 20 μm × 20 μm area) is used to physically transfer features to a mold surface. The die is attached to an actuator capable of producing an elliptical tool-path, the dimensions of which are process dependent and enable the die to match velocity with the moving mold during contact to avoid dragging the nanostructured area along the mold surface (smear). Nanocoining process parameters are discussed which enable indents to be indexed precisely to completely cover target areas. Techniques for die alignment and depth control are also required to create large areas (339 mm2) of nanofeatures in short times (∼20 min). Nanocoining experiments were performed at 1 kHz (1000 indents or 1.6 million features per second) on a flat electroless nickel sample. UV curable replicates were then created from the nickel mold and both the mold and replicate were examined in an SEM and AFM.}, number={41}, journal={NANOTECHNOLOGY}, author={Zdanowicz, Erik and Dow, Thomas A. and Scattergood, Ronald O.}, year={2012}, month={Oct} }
 @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{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{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{purohit_sun_shenderova_scattergood_brenner_2011, title={First-principles-based mesoscale modeling of the solute-induced stabilization of < 1 0 0 > tilt grain boundaries in an Al-Pb alloy}, volume={59}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2011.07.056}, abstractNote={A first-principles disclination structural units (DSUM) model was used to calculate the energies of 12 〈0 0 1〉 symmetric tilt grain boundaries in Al for a pure system and a system in which Pb atoms substitute for Al at one-half of the lattices sites along the interfacial plane. The grain boundaries are modeled as disclination dipole walls with energies given as a weighted sum of individual disclination energies determined from special low-sigma structures, elastic terms and disclination core energies. Predictions of the DSUM using the bulk Al shear modulus and Poisson’s ratio in the elastic and core energy terms are found to be comparable to energies for fully atomistic simulations calculated using a modified embedded-atom method (MEAM) potential. No relation between grain boundary energies in pure Al and the degree of stabilization due to Pb doping was found. The DSUM parameterized to density functional theory calculations predicts a ∼50% reduction in the energy anisotropy with respect to angle due to doping compared to the pure system, while MEAM calculations yield no appreciable reduction in the energy anisotropy.}, number={18}, journal={ACTA MATERIALIA}, author={Purohit, Y. and Sun, L. and Shenderova, O. and Scattergood, R. O. and Brenner, D. W.}, year={2011}, month={Oct}, pages={7022–7028} }
 @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{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{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{purohit_sun_irving_scattergood_brenner_2010, title={Computational study of the impurity induced reduction of grain boundary energies in nano- and bi-crystalline Al-Pb alloys}, volume={527}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2009.11.034}, abstractNote={Abstract Segregation of impurities with limited solubilities to grain boundaries can slow or even eliminate grain growth in nanocrystalline materials. Due to a very limited miscibility Pb is a potential candidate for thermodynamically stabilizing nanocrystalline Al. To investigate this we have used atomic modeling to characterize the structure and energy of substitutional Pb defects in bulk Al, in Al bi-crystals and in an Al nanocrystal. Monte Carlo simulations using a modified embedded-atom method (MEAM) potential fit to the results of density functional theory (DFT) calculations predict the formation of Pb clusters, in agreement with prior experiments. In addition, the simulations show strong segregation of Pb atoms to grain boundaries, a result that supports prior suggestions that Pb is distributed along grain boundaries in nanocrystals created by ball milling. Analysis of the enthalpies for Pb defects using MEAM and DFT calculations suggests that Pb impurities can help stabilize nanocrystalline Al against grain growth.}, number={7-8}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Purohit, Y. and Sun, L. and Irving, D. L. and Scattergood, R. O. and Brenner, D. W.}, year={2010}, month={Mar}, pages={1769–1775} }
 @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{shi_lane_mooney_dow_scattergood_2010, title={Diamond tool wear measurement by electron-beam-induced deposition}, volume={34}, ISSN={["1873-2372"]}, DOI={10.1016/j.precisioneng.2010.03.009}, abstractNote={Quantitative characterization of a diamond tool profile is critical to reveal tool wear mechanisms. An electron-beam-induced deposition (EBID) method reported previously is further developed and improved to measure diamond tool profiles using a field emission scanning electron microscope (SEM). The edge radius and wear land length for new and worn diamond tools were derived from analysis of the EBID-SEM images. Experimental results are presented to show that the methodology is an effective means to characterize diamond tool wear.}, number={4}, journal={PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY}, author={Shi, M. and Lane, B. and Mooney, C. B. and Dow, T. A. and Scattergood, R. O.}, year={2010}, month={Oct}, pages={718–721} }
 @article{lane_shi_dow_scattergood_2010, title={Diamond tool wear when machining Al6061 and 1215 steel}, volume={268}, ISSN={0043-1648}, url={http://dx.doi.org/10.1016/j.wear.2010.02.019}, DOI={10.1016/j.wear.2010.02.019}, abstractNote={Different rates of wear of diamond tools depend on the physical and chemical nature of the workpiece material. Wear mechanisms for diamond tools can be either abrasive or chemical in nature, or a combination thereof. Differentiating the affects of these wear mechanisms can be accomplished by measuring the wear geometry of the cutting edge as a function of cutting distance. Orthogonal cutting experiments using 6061 aluminum and 1215 steel were conducted to illustrate abrasive and abrasive plus chemical wear, respectively. Wear of the diamond tool was measured using the electron beam induced deposition method. This method provides nanometer resolution images of the tool edge (edge radius and wear land) that can be used to calculate volumetric wear loss and wear rates. A method for determining the Archard wear coefficient for diamond turning based on measured wear and cutting forces is also introduced. Comparisons are made between the tool wear resulting from the two materials, and hypotheses related to the wear mechanism are presented.}, number={11-12}, journal={Wear}, publisher={Elsevier BV}, author={Lane, B.M. and Shi, M. and Dow, T.A. and Scattergood, R.}, year={2010}, month={May}, pages={1434–1441} }
 @article{osetsky_scattergood_serra_stoller_2010, title={Elasticity to Atomistics: Predictive Modeling of Defect Behavior Symposium within MMM4 (October 2008) Dedicated to David Bacon PREFACE}, volume={90}, ISSN={["1478-6435"]}, DOI={10.1080/14786430903236040}, number={7-8}, journal={PHILOSOPHICAL MAGAZINE}, author={Osetsky, Yuri and Scattergood, Ron and Serra, Anna and Stoller, Roger}, year={2010}, pages={803–804} }
 @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{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{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{purohit_jang_irving_padgett_scattergood_brenner_2008, title={Atomistic modeling of the segregation of lead impurities to a grain boundary in an aluminum bicrystalline solid}, volume={493}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2007.05.128}, abstractNote={Using Monte Carlo simulations, new insights into the atomic segregation of lead (Pb) impurities to a Σ5 〈1 0 0〉 {2 1 0} tilt aluminum (Al) grain boundary have been obtained. Interatomic interactions in the Al–Pb alloy system were described using a modified embedded atom method potential with parameters that fit to the results of density functional calculations. The simulations predict segregation of Pb impurities along the Al grain boundary prior to the formation of Pb clusters. Analyses of grain boundary energies for varying concentrations of Pb suggests that grain boundaries in Al can be thermodynamically stabilized by Pb impurities with respect to a dilute solid solution of Pb in Al.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Purohit, Y. and Jang, S. and Irving, D. L. and Padgett, C. W. and Scattergood, R. O. and Brenner, D. W.}, year={2008}, month={Oct}, pages={97–100} }
 @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{jang_purohit_irving_padgett_brenner_scattergood_2008, title={Influence of Pb segregation on the deformation of nanocrystalline Al: Insights from molecular simulations}, volume={56}, ISSN={["1359-6454"]}, DOI={10.1016/j.actamat.2008.05.024}, abstractNote={Molecular dynamics straining simulations using a two-dimensional columnar model were run for pure Al with grain sizes from 5 to 30 nm, and for 10 nm grain size Al–Pb alloys containing 1, 2 and 3 at.% Pb. Monte Carlo simulations showed that all the Pb atoms segregate to the grain boundaries. Pb segregation suppresses the nucleation of partial dislocations and twins during straining. At 3 at.% Pb, no dislocations or twins are observed throughout the straining history. It also appeared that Pb tends to segregate to the same locations in grain boundaries that were favorable for partial dislocation emission. Grain boundaries with Pb segregates were very robust against dissociation during straining compared to pure Al. The yield stress determined from stress–strain curves showed a decrease with increasing Pb content, supporting a similar observation for the hardness change measured on nanocrystalline Al–Pb alloys.}, number={17}, journal={ACTA MATERIALIA}, author={Jang, S. and Purohit, Y. and Irving, D. L. and Padgett, C. and Brenner, D. and Scattergood, R. O.}, year={2008}, month={Oct}, pages={4750–4761} }
 @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{jang_purohit_irving_padgett_brenner_scattergood_2008, title={Molecular dynamics simulations of deformation in nanocrystalline Al-Pb alloys}, volume={493}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2007.05.130}, abstractNote={Abstract A modified embedded-atom method (MEAM) potential was developed and used for molecular dynamics (MD) straining simulations of Al–Pb alloys with a grain size of 10 nm and Pb content up to 3 at.%. Monte Carlo (MC) simulations done at 300 K indicated that all the Pb is segregated to the grain boundaries in these alloys. As the Pb content increases, partial dislocation nucleation at grain boundaries is suppressed, and the plastic strain is accommodated by mechanisms other than dislocation slip. The increasing Pb content was accompanied by a reduction in the yield and peak stress values.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Jang, S. and Purohit, Y. and Irving, D. and Padgett, C. and Brenner, D. and Scattergood, R. O.}, year={2008}, month={Oct}, pages={53–57} }
 @article{purohit_irving_scattergood_brenner_2008, title={Prediction of Energies of <100> Tilt Boundaries in Al-Pb Alloy}, volume={1056E}, journal={Materials Research Society Symposium Proceedings}, author={Purohit, Y. and Irving, D. L. and Scattergood, R. O. and Brenner, D. W.}, year={2008}, pages={1056–HH01-105610} }
 @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_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{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{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{qu_shih_scattergood_luo_2005, title={Abrasive micro-blasting to improve surface integrity of electrical discharge machined WC-Co composite}, volume={166}, ISSN={["1097-6787"]}, DOI={10.1016/j.jmatprotec.2004.09.075}, abstractNote={This study investigates the improvement of surface integrity of wire electrical discharge machined (EDM) WC–Co composite by abrasive micro-blasting. The thermally damaged recast layer generated by EDM has craters, cracks, and bubbles, which deteriorate the surface mechanical properties. The micro-blasting, using 6–12 and 4–20 μm size SiC abrasive, enables the removal of the recast layer and is suitable for micro mechanical components. The surface roughness of EDM rough cut WC–Co parts was improved significantly, with the average surface roughness (Ra) dropping down from 1.3 to 0.7 μm. Scanning electron microscope (SEM) was used to examine the evolution change of surface texture and subsurface cross-section of EDM WC–Co workpiece. The SEM micrographs showed that the recast layer was removed efficiently. After 5 s of micro-blasting, surface textures with ridge and cavity patterns were observed on fine and rough cut EDM surfaces, respectively. These surface textures could be correlated to the surface roughness measurement and crater formation in EDM spark erosion. A series of erosion wear experiment was conducted to quantify the weight reduction, calculate the erosion wear rate, and identify the wear mechanism.}, number={3}, journal={JOURNAL OF MATERIALS PROCESSING TECHNOLOGY}, author={Qu, J and Shih, AJ and Scattergood, RO and Luo, J}, year={2005}, month={Aug}, pages={440–448} }
 @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={Abstract}, 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} }
 @inbook{murty_kishore_yan_scattergood_helsel_2005, title={Effect of annealing temperature on texture and creep anisotropy in Ti3Al2.5V alloy}, volume={495-497}, DOI={10.4028/www.scientific.net/msf.495-497.1645}, abstractNote={Effect of annealing temperature is investigated on texture and creep anisotropy in a thinwalled tubing of titanium alloy. Creep anisotropy is studied under equibiaxial loading using internally pressurized tubing superimposed with axial load while monitoring in-situ the time variations of both hoop and axial strains. Relatively weak hoop direction in the cold-worked material became stronger following complete recrystallization. The analyses of the data reveal that the anisotropy parameter, P which is the contractile strain ratio for testing along hoop direction increases from around 0.6 for the cold-worked material to around 1.5 following complete recrystallization. Results indicate that planar isotropy should occur following annealing at around 800K. Work on the effects of annealing on the textures and deformation microstructures is in progress. We summarize here results from some of our earlier work on a different lot of Ti3Al2.5V tubing in the recrystallized states where the ODFs were used in conjunction with crystal slip models to predict creep anisotropy.}, booktitle={Textures of materials: ICOTOM 14: 
Proceedings of the 14th International Conference on Textures of Materials, held in Leuven, Belgium, July 11-15, 2005 / 
Paul van Houtte;  Leo Kestens. Uetikon-Zuerich, Switzerland ; Enfield, NH: Trans Tech Publications, 2005. (Materials science forum ; 495-497)}, publisher={Utikon-Zurich, Switzerland: Trans Tech Publications}, author={Murty, K. L. and Kishore, R. and Yan, J. and Scattergood, R. O. and Helsel, A. W.}, year={2005}, pages={1645–1650} }
 @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{bakkal_shih_mcspadden_liu_scattergood_2005, title={Light emission, chip morphology, and burr formation in drilling the bulk metallic glass}, volume={45}, ISSN={["1879-2170"]}, DOI={10.1016/j.ijmachtools.2004.11.004}, abstractNote={The chip light emission, chip morphology, burr formation and machined surface in drilling of Zr-based bulk metallic glass (BMG) material are investigated. This study demonstrates that the work- and tool-material as well as the feed rate and spindle speed, two drilling process parameters, all affect the onset of chip light emission. Slow feed rate and high spindle speed increase the specific cutting energy and promote the exothermic oxidation and light emission of the chip. Six types of chip morphology, powder, short ribbon, long ribbon, long spiral, long ribbon tangled, and fan, are observed in BMG drilling. The long ribbon tangled chip morphology is unique for BMG material. On the machined surface under quick stop condition, the fracture topography unique to metallic glass with tributary, void, and vein patterns is observed. Different burr formations are observed: the roll-over shape in the entry and the crown shape in the exit edge. The size of burr in the exit edge is typically larger than that in the entrance edge. High feed rate helps to reduce the size of burr in both entrance and exit edges. This study concludes that the WC–Co tool-material, due to its high thermal conductivity and hardness, performs better in drilling BMG than the high speed steel tool.}, number={7-8}, journal={INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE}, author={Bakkal, M and Shih, AJ and McSpadden, SB and Liu, CT and Scattergood, RO}, year={2005}, month={Jun}, pages={741–752} }
 @article{bakkal_shih_mcspadden_scattergood_2005, title={Thrust force, torque, and tool wear in drilling the bulk metallic glass}, volume={45}, ISSN={0890-6955}, url={http://dx.doi.org/10.1016/j.ijmachtools.2004.11.005}, DOI={10.1016/j.ijmachtools.2004.11.005}, abstractNote={The thrust force, torque, and tool wear in drilling of Zr-based bulk metallic glass (BMG) material are investigated. Drilling the BMG at high speed generates the chip light emission, high tool temperature, and severe tool wear. At low spindle speed, the BMG work-material builds up at the major and margin cutting edges and may break the drill. A range of feasible spindle speed and feed rate for the efficient drilling of BMG without the detrimental chip light emission and cutting edge work-material build-up has been identified in this study. Under the same drilling condition, the WC-Co tool generally requires less thrust force and about the same torque than the high-speed steel tool. The progressive wear of the major and margin cutting edges for BMG drilling is examined. Severe drill wear is associated with the bright BMG chip light emission. Without chip light emission, the drill wear is visible but not severe. This study concluded that precision holes in BMG could be generated with proper selection of tooling and process parameters.}, number={7-8}, journal={International Journal of Machine Tools and Manufacture}, publisher={Elsevier BV}, author={Bakkal, Mustafa and Shih, Albert J. and McSpadden, Samuel B. and Scattergood, Ronald O.}, year={2005}, month={Jun}, pages={863–872} }
 @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{bakkal_shih_scattergood_2004, title={Chip formation, cutting forces, and tool wear in turning of Zr-based bulk metallic glass}, volume={44}, ISSN={["1879-2170"]}, DOI={10.1016/j.ijmachtools.2004.02.002}, abstractNote={The chip light emission and morphology, cutting forces, surface roughness, and tool wear in turning of Zr-based bulk metallic glass (BMG) material are investigated. Machining results are compared with those of aluminum 6061-T6 and AISI 304 stainless steel under the same cutting conditions. This study demonstrates that the high cutting speeds and tools with low thermal conductivity and rake angle activate the light emission and chip oxidation in BMG machining. For the BMG chip without light emission, serrated chip formation with adiabatic shear band and void formation is observed. The cutting force analysis further correlates the chip oxidation and specific cutting energy and shows the significant reduction of cutting forces for machining BMG at high cutting speeds. The machined surface of BMG has better surface roughness than that of the other two work materials. Some tool wear features, including the welding of chip to the tool tip and chipping of the polycrystalline cubic boron nitride (PCBN) tool edge, are reported for turning of BMG. This study concludes that BMG can be machined with good surface roughness using conventional cutting tools.}, number={9}, journal={INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE}, author={Bakkal, M and Shih, AJ and Scattergood, RO}, year={2004}, month={Jul}, pages={915–925} }
 @article{bakkal_shih_scattergood_liu_2004, title={Machining of a Zr-Ti-Al-Cu-Ni metallic glass}, volume={50}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2003.11.052}, abstractNote={Zr52.5Ti5Cu17.9Ni14.6Al10 metallic glass machining chips were characterized using SEM, X-ray diffraction and nano-indentation. Above a threshold cutting speed, oxidation of the Zr produces high flash temperatures and causes crystallization. The chip morphology was unique and showed the presence of shear bands, void formation and viscous flow.}, number={5}, journal={SCRIPTA MATERIALIA}, author={Bakkal, M and Shih, AJ and Scattergood, RO and Liu, CT}, year={2004}, month={Mar}, pages={583–588} }
 @article{bakkal_liu_watkins_scattergood_shih_2004, title={Oxidation and crystallization of Zr-based bulk metallic glass due to machining}, volume={12}, DOI={10.1016/j.internet.2003.09.017}, number={2}, journal={Intermetallics}, author={Bakkal, M. and Liu, C. T. and Watkins, T. R. and Scattergood, R. O. and Shih, A. J.}, year={2004}, pages={195–204} }
 @article{bakkal_liu_watkins_scattergood_shih_2004, title={Oxidation and crystallization of Zr-based bulk metallic glass due to machining}, volume={12}, ISSN={0966-9795}, url={http://dx.doi.org/10.1016/j.intermet.2003.09.017}, DOI={10.1016/j.intermet.2003.09.017}, abstractNote={Bulk metallic glass was subjected to extreme deformation conditions during machining operation. The flash temperature, oxidation and crystallization within chips from a Zr-based bulk metallic glass were investigated. A near-infrared spectrometer was used to capture the light emission from the tool-chip interface allowing the calculation of the temperature. Very high temperatures in the 2400–2700 K range were observed and associated with the light emission and oxidation in the chips. X-ray diffraction analysis revealed oxidation of chips machined at high cutting speeds. Optical micrographs of polished and etched chip cross-sections showed a dendritic pattern due to crystallization. Using a field emission gun SEM, amorphous and crystalline regions were analyzed. This study demonstrates the oxidation and crystallization of bulk metallic glass during machining.}, number={2}, journal={Intermetallics}, publisher={Elsevier BV}, author={Bakkal, Mustafa and Liu, Chain T. and Watkins, Thomas R. and Scattergood, Ronald O. and Shih, Albert J.}, year={2004}, month={Feb}, pages={195–204} }
 @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{shih_scattergood_curry_yonushonis_gust_grant_mcspadden_watkins_2003, title={Cost-effective grinding of zirconia using the dense vitreous bond silicon carbide wheel}, volume={125}, ISSN={["1087-1357"]}, DOI={10.1115/1.1559167}, abstractNote={Results of grinding zirconia using wheels with fine grain size SiC and dense vitreous bond are presented. Wheel wear results demonstrated that this type of SiC wheel could grind fully and partially stabilized zirconia (PSZ) very effectively. X-ray diffraction was used to analyze the percentage of monoclinic phase in the PSZ base material, ground surface, and debris. As expected, due to the stress- and temperature-induced phase transformation during grinding, the percentage of monoclinic phase on the ground surface was increased relative to the base material. However, X-ray diffraction showed no monoclinic phase in the PSZ debris. This suggests that, during grinding, the low thermal conductivity of zirconia and SiC, compared to that of diamond, facilitates heat retention in the chip and softens the work-material. This makes the efficient grinding of PSZ possible. Grinding temperature measurement results supported this hypothesis.}, number={2}, journal={JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME}, author={Shih, AJ and Scattergood, RO and Curry, AC and Yonushonis, TM and Gust, DJ and Grant, MB and McSpadden, SB and Watkins, TR}, year={2003}, month={May}, pages={297–303} }
 @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{garrell_shih_lara-curzio_scattergood_2003, title={Finite-element analysis of stress concentration in ASTM D 638 tension specimens}, volume={31}, number={1}, journal={Journal of Testing and Evaluation}, author={Garrell, M. G. and Shih, A. J. and Lara-Curzio, E. and Scattergood, R. O.}, year={2003}, month={Jan}, pages={52–57} }
 @article{curry_shih_kong_scattergood_mcspadden_2003, title={Grinding temperature measurements in magnesia-partially-stabilized zirconia using infrared spectrometry}, volume={86}, ISSN={["1551-2916"]}, DOI={10.1111/j.1151-2916.2003.tb00019.x}, abstractNote={Results of temperature measurements by analysis of the thermal emission spectra generated during grinding and subsequently transmitted through partially stabilized zirconia workpieces are presented. Portions of emitted visible and near‐infrared spectra were collected with spectrometers. Source temperatures were determined by fitting the scaled spectrometer output spectra to blackbody curves. Simulations showed that the effective temperatures determined by this method will be strongly biased toward hot‐spot (flash) temperatures, which are expected to occur at the grinding grit–workpiece interface. Hot‐spot temperatures on the order of 3000 K were obtained for grinding with both SiC and diamond wheels. These high temperatures modify the grinding process and the phase content of grinding chips.}, number={2}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Curry, AC and Shih, AJ and Kong, J and Scattergood, RO and McSpadden, SB}, year={2003}, month={Feb}, pages={333–341} }
 @article{garrell_shih_ma_lara-curzio_scattergood_2003, title={Mechanical properties of Nylon bonded Nd-Fe-B permanent magnets}, volume={257}, ISSN={["0304-8853"]}, DOI={10.1016/S0304-8853(02)00983-6}, abstractNote={Tensile and flexural strengths as well as Young's modulus of Polyamide-11 (Nylon-11) based injection molded Nd–Fe–B magnets have been determined from −40°C to 100°C. Two types of Nd–Fe–B powders were included in this study. One is the conventional melt spun powder of irregular shape, the other is the atomized powder of spherical morphology. It was found that the tensile strength varies significantly with both test temperature and morphology of Nd–Fe–B powder. For a fixed volume fraction of magnet powder, the tensile strength decreases with increasing temperature. For bonded magnets made of melt spun powder, the tensile strength increases with increasing volume fraction of magnet powder. Specimens made of spherical atomized powders exhibit much lower tensile strength and better flexibility when compared to those made of melt spun powder. Scanning electron microscopy (SEM) analysis indicated that the debonding at the Nd–Fe–B powder and Nylon interface is the main cause of failure at 23°C and 100°C. At −40°C, a different failure mechanism with the fracture of Nd–Fe–B particle was observed on magnets prepared from melt spun powders. For the specimen containing 59.7 vol% of melt spun powder, a bending strength of 41 MPa and dynamic Young's modulus of 12.7 GPa were obtained.}, number={1}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Garrell, MG and Shih, AJ and Ma, BM and Lara-Curzio, E and Scattergood, RO}, year={2003}, month={Feb}, pages={32–43} }
 @article{garrell_ma_shih_lara-curzio_scattergood_2003, title={Mechanical properties of polyphenylene-sulfide (PPS) bonded NdFe-B permanent magnets}, volume={359}, ISSN={["0921-5093"]}, DOI={10.1016/s0921-5093(03)00400-3}, abstractNote={Mechanical properties, namely tensile and flexural strengths and elastic modulus, of polyphenylene-sulfide (PPS) bonded Nd–Fe–B magnets have been studied from −40 to 180 °C. The ultimate tensile strength (Sut) of PPS bonded magnets decreases with increasing temperature. The tensile strength of PPS bonded Nd–Fe–B magnets was reduced significantly above 100 °C. At 180 °C, the PPS bonded magnets still exhibit a Sut of 16–18 MPa. For bonded magnets with about 60% volume fraction of Nd–Fe–B powder, the PPS bonded magnet shows about twice the tensile strength and half the ultimate strain compared to that of Nylon bonded magnet. At room temperature, the flexural strength is, in general, comparable to the tensile strength. Dynamic elastic modulus measured using the impact resonance method was in good agreement with the elastic modulus obtained from tensile tests. Scanning Electron Microscopy analyses of the fractured surfaces revealed two distinct failure mechanisms. Debonding along the Nd–Fe–B particle and PPS interface is the main cause for failures at 100 and 180 °C. The fracture of Nd–Fe–B particle was observed on the fracture surface of specimens tested at −40 and 23 °C.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Garrell, MG and Ma, BM and Shih, AJ and Lara-Curzio, E and Scattergood, RO}, year={2003}, month={Oct}, pages={375–383} }
 @article{qu_riester_shih_scattergood_lara-curzio_watkins_2003, title={Nanoindentation characterization of surface layers of electrical discharge machined WC-Co}, volume={344}, ISSN={["0921-5093"]}, DOI={10.1016/s0921-5093(02)00395-7}, abstractNote={This study applies nanoindentation and other analysis techniques to investigate the influence of wire electrical discharge machining (EDM) process on the structure and properties of machined surface layers of WC–Co composites. Multiple indents were conducted on the cross-section of the surface recast layer, sub-surface heat-affected zone, and bulk material. The energy disperse X-ray spectrometry and X-ray diffraction were used to analyze the material compositions in the heat-affected zone and recast layer and to study the electrical spark eroded surface. The indents were inspected by scanning electron microscopy to distinguish between regular and irregular indents in these three regions. Irregular indents were caused by the porosity, soft matrix material, separation of grain boundaries, and thermal cracks caused by EDM process. The hardness and modulus of elasticity obtained from regular indents in bulk material and heat-affected zone were comparable to those of WC. It was found that the recast layer had lower hardness and modulus of elasticity than the bulk material and heat-affected zone.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Qu, J and Riester, L and Shih, AJ and Scattergood, RO and Lara-Curzio, E and Watkins, TR}, year={2003}, month={Mar}, pages={125–131} }
 @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{qu_shih_scattergood_2002, title={Development of the cylindrical wire electrical discharge machining process, part 1: Concept, design, and material removal rate}, volume={124}, ISSN={["1528-8935"]}, DOI={10.1115/1.1475321}, abstractNote={Results of applying the wire Electrical Discharge Machining (EDM) process to generate precise cylindrical forms on hard, difficult-to-machine materials are presented. The design of a precise, flexible, and corrosion-resistant underwater rotary spindle is first introduced. A detailed spindle error analysis identifies the major sources of error at different frequency spectrum. The spindle has been added to a conventional two-axis wire EDM machine to enable the generation of free-form cylindrical geometries. The mathematical model for material removal rate of the free-form cylindrical wire EDM process is derived. Experiments were conducted to explore the maximum material removal rate for cylindrical and 2D wire EDM of carbide and brass work-materials. Compared to the conventional 2D wire EDM of the same work-material, higher maximum material removal rates may be achieved in the cylindrical wire EDM, possibly due to better debris flushing condition.}, number={3}, journal={JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME}, author={Qu, J and Shih, AJ and Scattergood, RO}, year={2002}, month={Aug}, pages={702–707} }
 @article{qu_shih_scattergood_2002, title={Development of the cylindrical wire electrical discharge machining process, part 2: Surface integrity and roundness}, volume={124}, ISSN={["1087-1357"]}, DOI={10.1115/1.1475989}, abstractNote={This study investigates the surface integrity and roundness of parts created by the cylindrical wire EDM process. A mathematical model for the arithmetic average surface roughness on the ideal surface of a cylindrical wire EDM workpiece is first derived. Effects of wire feed rate and part rotational speed on the surface finish and roundness for brass and carbide work-materials at high material removal rates are investigated. The pulse on-time and wire feed rate are varied to explore the best possible surface finish and roundness achievable by the cylindrical wire EDM process. This study has demonstrated that, for carbide parts, an arithmetic average surface roughness and roundness as low as 0.68 and 1.7 μm, respectively, can be achieved. Surfaces of the cylindrical EDM parts were examined using Scanning Electron Microscopy (SEM) to identify the macro-ridges and craters on the surface. Cross-sections of the EDM parts are examined using the SEM to quantify the sub-surface recast layers and heat-affected zones under various process parameters. This study has demonstrated that the cylindrical wire EDM process parameters can be adjusted to achieve either high material removal rate or good surface integrity and roundness.}, number={3}, journal={JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME}, author={Qu, J and Shih, AJ and Scattergood, RO}, year={2002}, month={Aug}, pages={708–714} }
 @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={Abstract 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_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{rhoney_shih_scattergood_ott_mcspadden_2002, title={Wear mechanism of metal bond diamond wheels trued by wire electrical discharge machining}, volume={252}, ISSN={["0043-1648"]}, DOI={10.1016/S0043-1648(02)00019-4}, abstractNote={The stereographic scanning electron microscopy (SEM) imaging was used to investigate the wear mechanism in wire electrical discharge machining (EDM) truing of metal bond diamond wheels for ceramic grinding. A piece of the grinding wheel was removed after truing and grinding to enable the examination of wheel surface and measurement of diamond protrusion heights using a SEM and stereographic imaging software. The stereographic SEM imaging method was calibrated by comparing with the profilometer measurement results. On the wheel surface after wire EDM truing and before grinding, some diamond grain protruding heights were measured in the 32 μm level. Comparing to the 54 μm average size of the diamond grain, this indicated that over half of the diamond was exposed. During the wire EDM process, electrical sparks occur between the metal bond and EDM wire, which leaves the diamond protruded in the gap between the wire electrode and wheel. These protruding diamond grains with weak bond to the wheel were fractured under a light grinding condition. After heavy grinding, the diamond protrusion heights were estimated in the 5–15 μm range above the wear flat. A cavity created by grinding debris erosion wear of the wheel bond could be identified around the diamond grain.}, number={7-8}, journal={WEAR}, author={Rhoney, BK and Shih, AJ and Scattergood, RO and Ott, R and McSpadden, SB}, year={2002}, month={Apr}, pages={644–653} }
 @article{rhoney_shih_scattergood_akemon_gust_grant_2002, title={Wire electrical discharge machining of metal bond diamond wheels for ceramic grinding}, volume={42}, ISSN={["1879-2170"]}, DOI={10.1016/S0890-6955(02)00056-1}, abstractNote={The application of cylindrical wire Electrical Discharge Machining (EDM) for profile truing of metal bond diamond wheels is presented. Instead of using the mechanical force to break the diamond and matrix in the grinding wheel, the wire EDM process uses the thermal energy or electrical sparks between the wire and rotating grinding wheel to remove the metal bond and form the wheel. The design and manufacture of a corrosion-resistant, precise spindle with the high-electrical current capability for wire EDM truing of grinding wheel is first introduced. Three truing configurations were designed to study effects of wire EDM process parameters and to investigate the level of form accuracy and corner radii achievable by the wire EDM truing of diamond wheels. Results show that the wire EDM process can efficiently generate the μm-scale precision form on the diamond wheels. The wheel, after truing, was used to grind the silicon nitride workpiece. Grinding forces and wheel wear rate were measured. In the beginning of the grinding, high wheel wear rate was identified. The subsequent wheel wear rate was considerably lower and stabilized.}, number={12}, journal={INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE}, author={Rhoney, BK and Shih, AJ and Scattergood, RO and Akemon, JL and Gust, DJ and Grant, MB}, year={2002}, month={Sep}, pages={1355–1362} }
 @article{sharp_miller_scattergood_2000, title={Analysis of the grain depth-of-cut in plunge grinding}, volume={24}, ISSN={["0141-6359"]}, DOI={10.1016/S0141-6359(00)00032-5}, abstractNote={The grain depth-of-cut in plunge grinding was analyzed using computer simulation and an analytic model. Two regimes were identified for the depth-of-cut as a function of the infeed. At lower infeeds, there is a unique correlation between grinding grooves and cutting grains, and the depth-of-cut is equal to the infeed. At higher infeeds, the correlation is destroyed, and the depth-of-cut can be much less than the infeed. An analytic model that takes into account only the mean surface position while ignoring the surface profile can describe the latter regime.}, number={3}, journal={PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY}, author={Sharp, KW and Miller, MH and Scattergood, RO}, year={2000}, month={Jul}, pages={220–230} }
 @article{tanikella_gruss_davis_scattergood_1997, title={Indentation and microcutting fracture damage in a silicon carbide coating on an incoloy substrate}, volume={88}, DOI={10.1016/S0257-8972(96)02910-6}, abstractNote={The fracture damage morphology for static indentation tests and controlled microcutting tests using a Vickers indentor was investigated for an amorphous silicon carbide coating deposited on an Incoloy substrate. Crack initiation thresholds were detected for both testing modes using an acoustic emission sensor. The fracture damage morphology for static indentation consisted of Hertzian-like cracks surrounding the indentation site with no lateral crack-chipping occurring up to the maximum indentation load of 8 N. In contrast, microcutting generates lateral cracks at the microcutting groove entrance for loads as low as 0.3 N. For loads up to 1 N, the groove damage was confined to the 5 μm thick coating and the fracture response is similar to that occurring in a monolithic brittle solid. At higher loads, extensive lateral crack chipping occurred along the microcutting grooves accompanied by coating decohesion at the root of the chip.}, number={1-3}, journal={Surface & Coatings Technology}, author={Tanikella, B. V. and Gruss, K. A. and Davis, R. F. and Scattergood, R. O.}, year={1997}, pages={119–126} }
 @misc{roodposhti_sarkar_murty_scattergood, title={Effects of microstructure and processing methods on creep behavior of AZ91 magnesium alloy}, volume={25}, number={9}, journal={Journal of Materials Engineering and Performance}, author={Roodposhti, P. S. and Sarkar, A. and Murty, K. L. and Scattergood, R. O.}, pages={3697–3709} }
 @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} }