@article{ives_bui_habermann_collins_marsden_neilson_horn_rock_2023, title={1.5 MW CW RF Loads for Gyrotrons}, volume={277}, ISBN={["*****************"]}, ISSN={["2100-014X"]}, DOI={10.1051/epjconf/202327704008}, abstractNote={A new series of MW-class, RF loads were developed that can dissipate power levels exceeding 1.5 MW at frequencies from 28 GHz to 180 GHz. The new loads are designed to reflect less than 0.25% of the input power and operate continuously (CW). Stainless-steel and anodized aluminum versions were developed. The stainless steel version is designed to meet requirements for nuclear facilities, such as ITER, while the aluminum version is capable of power levels exceeding 2 MW CW. The aluminum version is also lighter and less expensive. This paper describes the design and capabilities of the loads.}, journal={21ST JOINT WORKSHOP ON ELECTRON CYCLOTRON EMISSION AND ELECTRON CYCLOTRON RESONANCE HEATING, EC21}, author={Ives, Lawrence and Bui, Thuc and Habermann, Thomas and Collins, George and Marsden, David and Neilson, Jeffrey and Horn, Tim and Rock, Chris}, year={2023} }
 @article{zhang_carriere_amoako_rock_thielk_fletcher_horn_2023, title={Microstructure and Elevated Temperature Flexure Testing of Tungsten Produced by Electron Beam Additive Manufacturing}, volume={8}, ISSN={["1543-1851"]}, DOI={10.1007/s11837-023-06045-5}, abstractNote={Abstract}, journal={JOM}, author={Zhang, Haozhi and Carriere, Paul R. and Amoako, Emmanuel D. and Rock, Chris D. and Thielk, Seiji U. and Fletcher, Colin G. and Horn, Timothy J.}, year={2023}, month={Aug} }
 @article{ovalle_rock_winkler_hartshorn_barr_cullom_tarafder_prost_white_anderson_et al._2023, title={Microstructure development and properties of micro-alloyed copper, Cu-0.3Zr-0.15Ag, produced by electron beam additive manufacturing}, volume={197}, ISSN={1044-5803}, url={http://dx.doi.org/10.1016/j.matchar.2023.112675}, DOI={10.1016/j.matchar.2023.112675}, abstractNote={A micro-alloyed copper powder, Cu-0.3Zr-0.15Ag wt%, was produced using gas atomization reaction synthesis. Zirconium was added to copper to sequester the oxygen present as copper oxide surface films on the powder particles. The as-received powders, as well as the intentionally oxidized powders were used to fabricate solid test articles by electron beam powder bed fusion additive manufacturing. Dense samples fabricated from as-received powder demonstrated nominal UTS, yield, and elongation values at 260 MPa, 150 MPa, and 34%, respectively. The average electrical conductivity of these samples was measured at 95% of the international annealed copper standard (IACS). Samples fabricated from the oxidized powder exhibited nominal UTS, yield, and elongation of 241 MPa, 146 MPa, and 43%, respectively, with an electrical conductivity of 95% IACS. During characterization, it was observed that, rather than forming nano-scale dispersoids, the Zirconia (ZrO2) appeared as discontinuous stringers in the metallographic cross-sections that crossed grain and melt pool boundaries. This was rationalized by tracing the presence of the micro-alloying addition of elemental zirconium, which was found to react with surface oxides dissociated in the melt pool to form ZrO2, which then solidified on the surface of the melt pool through an allotropic transformation to monoclinic ZrO2 in discontinuous films and spheroids ranging in size from nanometers to microns. This was confirmed by microscopic analysis of the tops of the melt pools. On subsequent melt passes, these ZrO2 structures were displaced and redistributed within the melt pool.}, journal={Materials Characterization}, publisher={Elsevier BV}, author={Ovalle, Denysse Gonzalez and Rock, Christopher and Winkler, Christopher and Hartshorn, Devin and Barr, Chris and Cullom, Tristan and Tarafder, Prithwish and Prost, Tim and White, Emma and Anderson, Iver and et al.}, year={2023}, month={Mar}, pages={112675} }
 @article{saptarshi_dejong_rock_anderson_napolitano_forrester_lapidus_kaoumi_horn_2022, title={Laser Powder Bed Fusion of ODS 14YWT from Gas Atomization Reaction Synthesis Precursor Powders}, volume={8}, ISSN={["1543-1851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85135355752&partnerID=MN8TOARS}, DOI={10.1007/s11837-022-05418-6}, abstractNote={Abstract}, journal={JOM}, author={Saptarshi, Sourabh and DeJong, Matthew and Rock, Christopher and Anderson, Iver and Napolitano, Ralph and Forrester, Jennifer and Lapidus, Saul and Kaoumi, Djamel and Horn, Timothy}, year={2022}, month={Aug} }
 @article{horn_rock_kaoumi_anderson_white_prost_rieken_saptarshi_schoell_dejong_et al._2022, title={Laser powder bed fusion additive manufacturing of oxide dispersion strengthened steel using gas atomized reaction synthesis powder}, volume={216}, ISSN={["1873-4197"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85127141491&partnerID=MN8TOARS}, DOI={10.1016/j.matdes.2022.110574}, abstractNote={Mechanically alloyed Fe-based alloys with oxide dispersion strengthening have largely dropped out of the marketplace due to high cost related to problems with complex and unreliable processing. Nevertheless, the desirable properties of oxide dispersion strengthened (ODS) steels have motivated research on alternate processing routes aimed at improving processing simplicity and reliability. Powders produced by gas atomization reaction synthesis (GARS) consist of stable Fe-Y intermetallic phases and a Cr surface oxide layer that acts as a chemical reservoir during solid-state processing and heat treatment to form a high density of nano-scale oxides. This research explores the use of Fe GARS powders, with 15 wt% Cr with micro-alloyed additions of 0.15 wt% Y and 0.10% Ti, in laser powder bed fusion (LPBF) additive manufacturing (AM), and evaluates the effectiveness of oxide dispersoid formation in the liquid melt pool. Additional oxygen was introduced by varying the LPBF chamber atmospheres using Ar, Ar + 1 wt% O, Ar + 5 wt% O, and air. Characterization of LPBF consolidated solids demonstrated the formation of a high density of nano-scale Y-Ti oxides in the build microstructures from the GARS precursor powders.}, journal={MATERIALS & DESIGN}, author={Horn, Timothy and Rock, Christopher and Kaoumi, Djamel and Anderson, Iver and White, Emma and Prost, Tim and Rieken, Joel and Saptarshi, Sourabh and Schoell, Ryan and DeJong, Matt and et al.}, year={2022}, month={Apr} }
 @article{rock_tarafder_ives_horn_2021, title={Characterization of copper & stainless steel interface produced by electron beam powder bed fusion}, volume={212}, ISSN={["1873-4197"]}, DOI={10.1016/j.matdes.2021.110278}, abstractNote={Unalloyed copper (Cu) powder was deposited and melted onto a pre-existing stainless steel substrate using electron beam powder bed fusion (EB-PBF) additive manufacturing (AM) to form dense, bimetallic structures. The AM fabricated Cu was fully dense, and with strength properties consistent with recent reports on EB-PBF of Cu. The overall bimetallic structures exhibited total elongation of 25–35%, and was dominated by plastic deformation in the Cu region. Tensile failures were typically observed in the Cu portion of the bimetallic bodies demonstrating that the interface was not the source of mechanical failure. The interface region of the bimetallics contained areas of liquid phase separated Cu and Iron (Fe) + Chromium (Cr) rich regions resulting from a metastable miscibility gap in the Cu and Fe phase diagram. Metallurgical and mechanical examinations of the bimetallic structures showed the interface region transitions from an Fe rich mixture to a Cu rich mixture within a few AM layers.}, journal={MATERIALS & DESIGN}, author={Rock, Christopher and Tarafder, Prithwish and Ives, Lawrence and Horn, Timothy}, year={2021}, month={Dec} }
 @article{hamilton_ramesh_harrysson_rock_rivero_2021, title={Cryogenic mechanical alloying of aluminum matrix composites for powder bed fusion additive manufacturing}, volume={55}, ISSN={["1530-793X"]}, DOI={10.1177/0021998320957698}, abstractNote={ Cryogenic mechanical alloying (cryomilling) was employed to fabricate aluminum matrix composite powder feedstock for additive manufacturing. The high energy milling of the powder system induces a homogenous distribution of reinforcement particles in the matrix powder by recurrent fracture and cold welding. In this study, aluminum matrix composite feedstock were produced via different cryomilling techniques at varying compositions, powder charges, and milling times. As-milled powders were characterized for particle size distribution, morphology, and homogeneity. Resultant powder demonstrated varying characteristics correlated to milling parameters. Powder metallurgy samples were also fabricated to understand as-sintered reinforcement distribution and the resultant strengthening. This research provides an indication of cryomilling capabilities to become an effective method for custom alloy powder production for powder bed fusion additive manufacturing. }, number={5}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Hamilton, Jakob D. and Ramesh, Srikanthan and Harrysson, Ola L. A. and Rock, Christopher D. and Rivero, Iris V}, year={2021}, month={Mar}, pages={641–651} }
 @article{hankwitz_ledford_rock_o'dell_horn_2021, title={Electron Beam Melting of Niobium Alloys from Blended Powders}, volume={14}, ISSN={["1996-1944"]}, DOI={10.3390/ma14195536}, abstractNote={Niobium-based tungsten alloys are desirable for high-temperature structural applications yet are restricted in practice by limited room-temperature ductility and fabricability. Powder bed fusion additive manufacturing is one technology that could be leveraged to process alloys with limited ductility, without the need for pre-alloying. A custom electron beam powder bed fusion machine was used to demonstrate the processability of blended Nb-1Zr, Nb-10W-1Zr-0.1C, and Nb-20W-1Zr-0.1C powders, with resulting solid optical densities of 99+%. Ultimately, post-processing heat treatments were required to increase tungsten diffusion in niobium, as well as to attain satisfactory mechanical properties.}, number={19}, journal={MATERIALS}, author={Hankwitz, Jameson P. and Ledford, Christopher and Rock, Christopher and O'Dell, Scott and Horn, Timothy J.}, year={2021}, month={Oct} }
 @article{ellis_sprayberry_ledford_hankwitz_kirka_rock_horn_katoh_dehoff_2021, title={Processing of tungsten through electron beam melting *}, volume={555}, ISSN={["1873-4820"]}, DOI={10.1016/j.jnucmat.2021.153041}, abstractNote={Additive manufacturing (AM) presents a new design paradigm for the manufacture of engineering materials through the layer-by-layer approach combined with welding theory. In the instance of difficult to process materials such as tungsten and other refractory metals, AM offers an opportunity for radical redesign of critical components for next-generation energy technologies including fusion. In this work, electron beam powder bed fusion (EB-PBF) is applied to process pure tungsten to study the influence of process parameters on the defect density of the material. An in-situ image analysis algorithm is applied to pure tungsten for the first time, and is used to visualize the defect structure in AM tungsten. Finally, a cracking mechanism for AM tungsten is proposed, and suggestions for suppression of cracks in pure tungsten are offered.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Ellis, Elizabeth A. I. and Sprayberry, Michael A. and Ledford, Christopher and Hankwitz, Jameson P. and Kirka, Michael M. and Rock, Chris D. and Horn, Timothy J. and Katoh, Yutai and Dehoff, Ryan R.}, year={2021}, month={Nov} }
 @article{tarafder_rock_horn_2021, title={Quasi-Static Tensile Properties of Unalloyed Copper Produced by Electron Beam Powder Bed Fusion Additive Manufacturing}, volume={14}, ISSN={["1996-1944"]}, DOI={10.3390/ma14112932}, abstractNote={Mechanical properties of powder bed fusion processed unalloyed copper are reported majorly in the as-fabricated condition, and the effect of post-processes, common to additive manufacturing, is not well documented. In this study, mechanical properties of unalloyed copper processed by electron beam powder bed fusion are characterized via room temperature quasi-static uniaxial tensile test and Vickers microhardness. Tensile samples were extracted both perpendicular and parallel to the build direction and assigned to three different conditions: as-fabricated, hot isostatic pressing (HIP), and vacuum annealing. In the as-fabricated condition, the highest UTS and lowest elongation were obtained in the samples oriented perpendicular to the build direction. These were observed to have clear trends between sample orientation caused primarily by the interdependencies between the epitaxial columnar grain morphology and dislocation movement during the tensile test. Texture was insignificant in the as-fabricated condition, and its effect on the mechanical properties was outweighed by the orientation anisotropy. The fractographs revealed a ductile mode of failure with varying dimple sizes where more shallow and finely spaced dimples were observed in the samples oriented perpendicular to the build direction. EDS maps reveal that grain boundary oxides coalesce and grow in HIP and vacuum-annealed specimens which are seen inside the ductile dimples and contribute to their increased ductility. Overall, for the post-process parameters chosen in this study, HIP was observed to slightly increase the sample’s density while vacuum annealing reduced the oxygen content in the specimens.}, number={11}, journal={MATERIALS}, author={Tarafder, Prithwish and Rock, Christopher and Horn, Timothy}, year={2021}, month={Jun} }
 @article{rock_ledford_garcia-avila_west_miller_pankow_dehoff_horn_2021, title={The Influence of Powder Reuse on the Properties of Nickel Super Alloy ATI 718 (TM) in Laser Powder Bed Fusion Additive Manufacturing}, volume={52}, ISSN={["1543-1916"]}, DOI={10.1007/s11663-020-02040-2}, number={2}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE}, author={Rock, Christopher and Ledford, Christopher and Garcia-Avila, Matias and West, Harvey and Miller, Victoria M. and Pankow, Mark and Dehoff, Ryan and Horn, Tim}, year={2021}, month={Apr}, pages={676–688} }
 @article{rock_lara-curzio_ellis_ledford_leonard_kannan_kirka_horn_2020, title={Additive Manufacturing of Pure Mo and Mo plus TiC MMC Alloy by Electron Beam Powder Bed Fusion}, volume={72}, ISSN={["1543-1851"]}, DOI={10.1007/s11837-020-04442-8}, abstractNote={A metal matrix composite powder of molybdenum (Mo) + TiC was produced by mechanical alloying (MA) and used in additive manufacturing by electron beam powder bed fusion along with pure Mo powder to form sandwich structures. The Mo + TiC solid layers formed mixed structures of Mo with discrete TiC particles, eutectic Mo + TiC, and Mo dendrites. Thermodynamic modeling showed that the system contained an invariant eutectic reaction in the composition range used and indicated that the system was highly sensitive to changes in composition and temperature.}, number={12}, journal={JOM}, author={Rock, Christopher and Lara-Curzio, Edgar and Ellis, Betsy and Ledford, Christopher and Leonard, Donovan N. and Kannan, Rangasayee and Kirka, Michael and Horn, Timothy}, year={2020}, month={Dec}, pages={4202–4213} }
 @article{rock_vadlakonda_figurskey_ledford_west_miller_pankow_daniels_horn_2020, title={Analysis of Self-Organized Patterned Surface Oxide Spots on Ejected Spatter Produced during Laser Powder Bed Fusion}, volume={35}, ISBN={2214-7810}, url={http://dx.doi.org/10.1016/j.addma.2020.101320}, DOI={10.1016/j.addma.2020.101320}, abstractNote={Spatter particles ejected from the melt pool after melting of 316 L stainless steel by laser powder bed fusion additive manufacturing (LPBF), were found to contain morphologies not observed in as-atomized 316 L powder. This spatter consisted of large, spherical particles, highly dendritic surfaces, particles with caps of accreted liquid, and agglomerations of multiple individual particles fixed together by liquid ligaments prior to solidification. The focus of this study is on an additional, unique spatter morphology consisting of larger, spherical particles with surface oxide spots exhibiting a wide distribution of surface configurations, including organized patterning. Spatter particles with organized surface oxide patterns were characterized for surface and internal particle features using multiple imaging techniques. The following observations are made: 1) spots resided at the spatter particle surface and did not significantly penetrate the interior, 2) the spot(s) were amorphous and rich in Silicon (Si)-Manganese (Mn)-Oxygen (O), 3) a two-part Chromium (Cr)-O rich layer exists between the particle and spot, 4) Cr-O rich morphological features were present at the top surface of the spots, 5) the spatter particle composition was consistent with 316 L but appeared to decrease in Si content into the spatter particle away from a spot, and 6) small Si-rich spherical particles existed within the spatter particle interior.}, journal={Additive Manufacturing}, publisher={Elsevier BV}, author={Rock, Christopher and Vadlakonda, Rashmi and Figurskey, Sullivan and Ledford, Christopher and West, Harvey and Miller, Victoria and Pankow, Mark and Daniels, Karen E. and Horn, Tim}, year={2020}, month={Oct}, pages={101320} }
 @article{ledford_rock_tung_wang_schroth_horn_2020, title={Evaluation of Electron Beam Powder Bed Fusion Additive Manufacturing of High Purity Copper for Overhang Structures Using In-Situ Real Time Backscatter Electron Monitoring}, volume={48}, ISSN={2351-9789}, url={http://dx.doi.org/10.1016/j.promfg.2020.05.120}, DOI={10.1016/j.promfg.2020.05.120}, abstractNote={Electron beam based additive manufacturing (AM) with copper must consider the high intrinsic thermal conductivity of copper as well as the greater difference between the thermal properties of the AM article and the surrounding or underlying powder bed. Successful processing requires multi-step control of the beam-bed interactions driven by a combination of a priori calculations and real-time monitoring and feedback to achieve melt pool size stability and appropriate bed/article temperatures as thermal boundary conditions vary based on geometry. The objective of this work is to utilize electron imaging to rapidly assess the processing space for copper with a wide shift in thermal boundary conditions using samples with overhang features. A modified commercial Arcam EBM AM system and process parameter space are described that allow successful AM of copper for complex geometries.}, journal={Procedia Manufacturing}, publisher={Elsevier BV}, author={Ledford, Chris and Rock, Chris and Tung, Mouda and Wang, Hongliang and Schroth, James and Horn, Timothy}, year={2020}, pages={828–838} }
 @article{ledford_tung_rock_horn_2020, title={Real time monitoring of electron emissions during electron beam powder bed fusion for arbitrary geometries and toolpaths}, volume={34}, ISSN={["2214-7810"]}, DOI={10.1016/j.addma.2020.101365}, abstractNote={Real-time monitoring of electron emissions during the operable processing steps of electron beam powder bed fusion (EB-PBF), which typically include preheating, melting, and post-heating, provides a wealth of in-process data across multiple length scales. In this paper, we present a methodology for collecting both real-time beam positional data and electron emissions as a function of time for arbitrary component geometries and complex toolpaths. To demonstrate this, we collected these data during the melting steps of EB-PBF of pure copper and quantitatively compared electron images generated with this approach to both x-ray micro computed tomography (μCT) data and optical micrographs of the same specimens. These results show a strong mathematical correlation between the location of loss of signal events observed in electron images and observed defects in μCT. At the same time, the collection of beam positional information facilitates the calculation of beam velocities, and hence local energy inputs. We also demonstrate a to methodology visualize process data from a wide variety of sources and map these over the 3D geometries as a function of time and position and to link these spatiotemporal data to structure observed in the electron imaging and energy input maps. Ultimately, we have leveraged this new electron imaging approach to defect detection into a rudimentary control strategy to eliminate porosity in a copper sample.}, journal={ADDITIVE MANUFACTURING}, author={Ledford, Christopher and Tung, Mouda and Rock, Chris and Horn, Timothy}, year={2020}, month={Aug} }
 @article{ledford_rock_carriere_frigola_gamzina_horn_2019, title={Characteristics and Processing of Hydrogen-Treated Copper Powders for EB-PBF Additive Manufacturing}, volume={9}, ISSN={["2076-3417"]}, DOI={10.3390/app9193993}, abstractNote={The fabrication of high purity copper using additive manufacturing has proven difficult because of oxidation of the powder feedstock. Here, we present work on the hydrogen heat treatment of copper powders for electron beam powder bed fusion (EB-PBF), in order to enable the fabrication of high purity copper components for applications such as accelerator components and vacuum electronic devices. Copper powder with varying initial oxygen contents were hydrogen heat-treated and characterized for their chemistry, morphology, and microstructure. Higher initial oxygen content powders were found to not only reduce surface oxides, but also reduce oxides along the grain boundaries and form trapped H2O vapor inside the particles. The trapped H2O vapor was verified by thermogravimetric analysis (TGA) and residual gas analysis (RGA) while melting. The mechanism of the H2O vapor escaping the particles was determined by in-situ SEM heated stage experiments, where the particles were observed to crack along the grain boundaries. To determine the effect of the EB-PBF processing on the H2O vapor, the thermal simulation and the validation of single melt track width wafers were conducted along with melting single layer discs for chemistry analysis. A high speed video of the EB-PBF melting was performed in order to determine the effect of the trapped H2O vapor on the melt pool. Finally, solid samples were fabricated from hydrogen-treated copper powder, where the final oxygen content measured ~50 wt. ppm, with a minimal residue hydrogen content, indicating the complete removal of trapped H2O vapor from the solid parts.}, number={19}, journal={APPLIED SCIENCES-BASEL}, author={Ledford, Christopher and Rock, Christopher and Carriere, Paul and Frigola, Pedro and Gamzina, Diana and Horn, Timothy}, year={2019}, month={Oct} }
 @article{white_rinko_prost_horn_ledford_rock_anderson_2019, title={Processing of Alnico Magnets by Additive Manufacturing}, volume={9}, ISSN={["2076-3417"]}, DOI={10.3390/app9224843}, abstractNote={Permanent magnets without rare earth (RE) elements, such as alnico, will improve supply stability and potentially decrease permanent magnet cost, especially for traction drive motors and other increased temperature applications. Commercial alnico magnets with the highest energy product are produced by directional solidification (DS) to achieve a <001> columnar grain orientation followed by significant final machining, adding to the high cost. Additive manufacturing (AM) is an effective method to process near net-shape parts with minimal final machining of complex geometries. AM also, has potential for texture/grain orientation control and compositionally graded structures. This report describes fabrication of alnico magnets by AM using both laser engineered net shaping (LENS)/directed energy deposition (DED) and electron beam melting powder bed fusion (EBM/PBF). High pressure gas atomized (HPGA) pre-alloyed alnico powders, with high purity and sphericity, were built into cylindrical and rectangular samples, followed by magnetic annealing (MA) and a full heat treatment (FHT). The magnetic properties of these AM processed specimens were different from their cast and sintered counterparts of the same composition and show a great sensitivity to heat treatment. The AM process parameters used in this developmental study did not yet result in any preferred texture within the alnico AM builds. These findings demonstrate feasibility for near net-shape processing of alnico permanent magnets for use in next generation traction drive motors and other applications requiring increased operating temperatures and/or complex engineered part geometries, especially with further AM process development for texture control.}, number={22}, journal={APPLIED SCIENCES-BASEL}, author={White, Emma and Rinko, Emily and Prost, Timothy and Horn, Timothy and Ledford, Christopher and Rock, Christopher and Anderson, Iver}, year={2019}, month={Nov} }
 @article{mahbooba_thorsson_unosson_skoglund_west_horn_rock_vogli_harrysson_2018, title={Additive manufacturing of an iron-based bulk metallic glass larger than the critical casting thickness}, volume={11}, ISSN={["2352-9407"]}, DOI={10.1016/j.apmt.2018.02.011}, abstractNote={Fe-based bulk metallic glasses (BMG) are of increasing research interest, driven in part by a unique combination of mechanical, magnetic and chemical properties. However, the maximum thickness and geometry of BMGs achievable in traditional manufacturing processes is limited. This work examines the capabilities of laser based powder bed additive manufacturing (AM) to produce relatively large Fe-based bulk metallic glass specimens. AM fabricated specimens exceed the critical casting thickness of the material by a factor of 15 or more in all dimensions. Resulting microstructural and mechanical properties are reported. Despite decreasing quench effect with increasing build thickness, X-ray diffraction analysis suggests that a fully amorphous structure was maintained throughout the build. However, a low concentration of sparsely distributed nano-grain clusters was discovered using a high-resolution electron backscatter diffraction scan. The results pave the way for novel applications of metallic glasses achievable through appropriate material design and optimization of existing additive manufacturing processes.}, journal={APPLIED MATERIALS TODAY}, author={Mahbooba, Zaynab and Thorsson, Lena and Unosson, Mattias and Skoglund, Peter and West, Harvey and Horn, Timothy and Rock, Christopher and Vogli, Evelina and Harrysson, Ola}, year={2018}, month={Jun}, pages={264–269} }
 @article{rock_qiu_okazaki_1998, title={Electro-Discharge of Nanocrystalline Nb-Al Powders Produced by Mechanical Alloying}, volume={33}, ISSN={0022-2461}, url={http://dx.doi.org/10.1023/A:1004386822343}, DOI={10.1023/A:1004386822343}, number={1}, journal={Journal of Materials Science}, publisher={Springer Science and Business Media LLC}, author={Rock, C and Qiu, Jun and Okazaki, K}, year={1998}, pages={241–246} }
 @article{qiu_shibata_rock_okazaki_1997, title={Electro-Discharge Consolidation of Atomized High Strength Aluminum Powders}, volume={38}, ISSN={0916-1821 2432-471X}, url={http://dx.doi.org/10.2320/matertrans1989.38.226}, DOI={10.2320/matertrans1989.38.226}, abstractNote={Electro-discharge consolidation (EDC) was carried out for atomized Al-based alloy powders produced at YKK. Input energies of 2.5 to 3.8 kJ/g produced compacts of 88 to 99% in theoretical density. The densification can be described by a simple relation of Δ P = 11.8[ER s /(R s +2)] 0.36 in % where R s is the specimen resistance, and it predominantly depends on input energy, E. A comparison of XRD spectra before and after EDC with respect to the peaks' position and intensity indicates that no microstructural change occurred. Oxide film removal by EDC was confirmed by TEM observations. Compression tests of EDC compacts at room temperature produced under the present conditions (specimen resistance R s = 9.4-15.8 mΩ) yielded 800 MPa and 24% elongation for true ultimate compressive stress and true compressive strain, respectively. The annealing treatment at 573 K for 1.2 ks raiseds compressive strength by at expense of ductility due to precipitation of solute atoms, indicating that a super-saturated solid solution is maintained in the EDC state.}, number={3}, journal={Materials Transactions, JIM}, publisher={Japan Institute of Metals}, author={Qiu, J. and Shibata, T. and Rock, C. and Okazaki, K.}, year={1997}, pages={226–231} }
 @article{qiu_rock_shibata_okazaki_1996, title={Mechanical Alloying of Al<sub>91</sub>Ni<sub>5</sub>Cu<sub>2</sub>Ti<sub>1.4</sub>Zr<sub>0.4</sub>Mm<sub>0.2</sub> Powders and Electro-Discharge Consolidation into Bulk}, volume={235-238}, ISSN={1662-9752}, url={http://dx.doi.org/10.4028/www.scientific.net/MSF.235-238.273}, DOI={10.4028/www.scientific.net/MSF.235-238.273}, journal={Materials Science Forum}, publisher={Trans Tech Publications, Ltd.}, author={Qiu, J. and Rock, C. and Shibata, Toshio and Okazaki, Kenji}, year={1996}, month={Oct}, pages={273–278} }
 @inproceedings{rock_okazaki_1996, place={Warrendale, Pennsylvania}, title={Phase Identification, Thermal Stability and Electro-Discharge Consolidation in a Mechanically Alloyed Nb-Al}, ISBN={9780873393355}, booktitle={Processing and properties of nanocrystalline materials}, publisher={TMS}, author={Rock, Christopher and Okazaki, Kenji}, editor={Suryanarayana, C. and Singh, J. and Froes, F.H.Editors}, year={1996}, pages={199} }
 @article{rock_okazaki_1995, title={Detailed phase analysis of a 77 at.%Nb-Al system prepared by low-energy ball milling}, volume={5}, ISSN={0965-9773}, url={http://dx.doi.org/10.1016/0965-9773(95)00282-J}, DOI={10.1016/0965-9773(95)00282-J}, abstractNote={Elemental powders of Nb (77 at.%) andAl (23 at.%) were alloyed in a low-energy ball mill for 360–1800 ks in hopes of forming a nanocrystalline intermetallic compound, Nb3Al. It was revealed by careful deconvolution of XRD spectra into various peaks of possibly existing phases that the resultant powder is a nanocrystalline multiphase mixture consisting of Nb3Al, Nb2Al, elemental Nb and Al, with their particulate sizes of approximately 5–8 nm, even after 1800 ks milling. The volume fractions of these phases were estimated to be 28.4, 39.5, 30.3 and 1.8 vol.%, respectively. The kinetic energy provided by ball-milling was insufficient to produce a single Nb3Al phase, and even heating to 933 K for 25.2 ks failed the total conversion of a multiphase mixture.}, number={6}, journal={Nanostructured Materials}, publisher={Elsevier BV}, author={Rock, C. and Okazaki, K.}, year={1995}, month={Aug}, pages={643–656} }
 @article{rock_okazaki_1995, title={Grain growth kinetics and thermal stability in a nanocrystalline multiphase mixture prepared by low-energy ball milling}, volume={5}, ISSN={0965-9773}, url={http://dx.doi.org/10.1016/0965-9773(95)00278-M}, DOI={10.1016/0965-9773(95)00278-M}, abstractNote={A multiphase powder mixture consisting of approximately 40 vol.% Nb2Al, 30 vol.% Nb, 28 vol.% Nb3Al and 2 vol.% Al with their crystallite sizes of approximately 5 to 8 nm was subjected in vacuum to elevated temperatures. The anneal at 1373 K for 25.2 ks produced a three phase mixture of Nb, Nb2Al, Al and Nb3Al, their volume fractions being 3.9, 4.8 and 91.3 vol.% and their ultimate paniculate sizes being 8.2, 13.8 and 36.0 nm, respectively. The detailed analysis of isothermal annealing from 973 to 1373 K for 3.6, 10.8 and 25.2 ks revealed complex grain growth kinetics for Nb2Al and Nb3Al phases with an exponent of n = 18 in D = ktn where D is grain size, k the growth constant and t annealing time. The analysis of grain growth data yielded a dual-stage activation energy of 68.2 ± 4 and 91.3 ± 6 kJmol for grain growth in Nb3Al below and above 1173 K, respectively. Likewise, the activation energy for grain growth in Nb2Al was found to be 62.8 ± 2 and 83.9 ± 7 kJmole below and above 1173 K, respectively.}, number={6}, journal={Nanostructured Materials}, publisher={Elsevier BV}, author={Rock, C. and Okazaki, K.}, year={1995}, month={Aug}, pages={657–671} }
 @inproceedings{rock_pete_okazaki_1993, title={Detailed Analysis of Phase Formation During Mechanical Alloying of Nb and Al}, volume={1}, booktitle={Proceedings of 1993 World Powder Metallurgy Congress, Japan Society of Powder and Powder Metallurgy}, author={Rock, C. and Pete, T. and Okazaki, K.}, year={1993}, pages={100} }
 @inproceedings{rock_okazaki_1993, title={Mechanical Grinding of 6 mol% Y2O3-ZrO2}, volume={1}, booktitle={Proceedings of 1993 World Powder Metallurgy Congress, Japan Society of Powder and Powder Metallurgy}, author={Rock, C. and Okazaki, K.}, year={1993}, pages={147} }