Edwards Air Force Base, CA, United States
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Pozuelo M.,University of California at Los Angeles | Melnyk C.,California Nanotechnologies Inc. | Kao W.H.,University of California at Los Angeles | Yang J.-M.,University of California at Los Angeles
Journal of Materials Research | Year: 2011

The microstructure characteristics of nanocrystalline magnesium-based alloy processed by cryomilling and spark plasma sintering were investigated. The as-received and cryomilled powders and the consolidated bulk material were characterized by scanning and transmission electron microscopies, x-ray diffraction, and electron dispersive spectroscopy techniques. The cryomilled powders resulted in an average grain size of 25 nm. After spark plasma sintering, a bimodal grain size distribution with coarse grains around 500 nm and fine grains of 52 nm, which is one of the smallest grain sizes reported in bulk nanostructured Mg alloys, was found. Our results suggest this novel process as a viable method to provide new opportunities for the development of nanostructured Mg-based alloys. © 2011 Materials Research Society.

Melnyk C.,California Nanotechnologies Inc. | Grant D.,California Nanotechnologies Inc. | Keener S.G.,Boeing Company | Gansert R.V.,Advanced Materials Technology, Inc. | Schroeder S.,University of Calgary
JOM | Year: 2011

Ultrafine grained materials consolidated using spark plasma sintering and hot isostatic pressing show great potential for applications in aerospace, energy, and a vast range of other industries. The Hall-Petch relationship cites the strengthening of materials by reducing the average crystallite (grain) size. A study is proposed to investigate the increase in mechanical properties provided by fine-grained, near-nano- and nano-crystalline powders produced from cryomilling and consolidation using spark plasma sintering (SPS) and hot isostatic pressing (HIPing). Initial testing indicates an increase in hardness and shear in commercially pure aluminum by 2-3 times from use of fine-grained, near-nano-, nano-crystalline materials. Cryomilled powders and consolidated forms of these powders will be examined using field emission scanning electron microscopy. Macrohardness, microhardness, tensile testing and shear testing will be performed to examine the mechanical properties. © 2011 TMS.

Melnyk C.,California Nanotechnologies Inc. | Weinstein B.,California Nanotechnologies Inc. | Lujan D.,California Nanotechnologies Inc. | Grant D.,California Nanotechnologies Inc. | Gansert R.,Advanced Materials Technology, Inc.
Advanced Materials and Processes | Year: 2011

Aerospace components in production volumes can be produced using nano-based materials. Nano-based components can be produced in high-volume operations by providing the material in wire and/or rod form for use in production cold and hot forging operations. For these production operations, the nano-based materials are consolidated into billets and produced into wire using traditional wire forming operations. Components produced from these nano-based light alloys and composites enable use in higher performance applications compared to conventional materials.

Xu C.,University of Southern California | Schroeder S.,California Nanotechnologies Inc. | Berbon P.B.,California Titanium | Langdon T.G.,University of Southern California | Langdon T.G.,University of Southampton
Acta Materialia | Year: 2010

Equal-channel angular pressing (ECAP) combined with the Conform process provides a solution for the continuous production of ultrafine-grained materials. Rods of a commercial Al-6061 alloy were processed by ECAP-Conform at room temperature for up to a total of four passes. Microstructural observations showed significant grain refinement but with elongated grains after four passes with average widths of ∼150 nm and lengths of ∼1.2 μm when viewed on the longitudinal planes. Microhardness measurements after a single pass revealed inhomogeneities both on the cross-sectional planes and along the rod. After processing through four passes there was reasonable homogeneity throughout the rod. Measurements of the shear strengths in two orthogonal directions perpendicular to the extrusion axis showed significant strengthening after ECAP-Conform and there was no evidence for any plastic anisotropy after processing through four passes. © 2009 Acta Materialia Inc.

Dheda S.S.,University of California at Irvine | Melnyk C.,California Nanotechnologies Inc. | Mohamed F.A.,University of California at Irvine
Materials Science and Engineering A | Year: 2013

In this work, titanium nitride (TiN) nanoparticles (~20. nm) were introduced during cryomilling of commercially pure titanium (CP Ti). Consolidation of cryomilled powders was performed using spark plasma sintering (SPS). Samples were analyzed and tested alongside cryomilled, SPS CP Ti not containing TiN nanoparticles. After cryomilling powders containing TiN nanoparticles and powders not containing TiN had a minimum grain size of ~20. nm. Microstructure analysis after thermal processing of both samples revealed that grain size retention occurred due to the presence of TiN nanoparticles in CP Ti microstructure. In consolidated samples containing 5. vol% TiN nanoparticles, the minimum average grain size was retained to ~250. nm, while in samples containing 0. vol% TiN nanoparticles, the minimum average grain size obtained was ~750. nm. Microhardness testing showed an increased hardness of samples containing TiN nanoparticles due to the retention of smaller grains and the presence of TiN nanoparticles. © 2013 Elsevier B.V.

Dheda S.S.,University of California at Irvine | Kim Y.K.,University of California at Irvine | Melnyk C.,California Nanotechnologies Inc. | Liu W.,University of California at Irvine | Mohamed F.A.,University of California at Irvine
Journal of Materials Science: Materials in Medicine | Year: 2013

Ti alloys, such as Ti6Al4V, are currently used in biomedical and dental implant applications. Ti alloys are used because they are stronger than commercially pure (CP) Ti due to the presence of alloying elements. However, toxicity of alloying elements during long-term use of implants is of concern. Another means of increasing the strength of materials is grain size refinement. In this study, ultrafine-grained (UFG, *250 nm to 1 μm) CP Ti was produced by cryomilling followed by spark plasma sintering (SPS). Electrochemical impedance spectroscopy (EIS) and cell culture experiments were performed to compare the corrosion and biocompatibility properties of coarse grained (CG) Ti and UFG Ti. It was found that UFG Ti exhibited corrosion resistance comparable to CG Ti in Ringers solution. In addition, UFG Ti exhibited a reduced inflammatory response and enhanced cell adhesion compared to CG Ti. Investigation of surface roughness provided an explanation for enhanced cell adhesion. © Springer Science+Business Media New York 2013.

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