Papers by Keyword: Nanocrystalline Metals

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Authors: Wei Liu, Qiong Hua Zhou
Abstract: Nanocrystalline nonferrous metals (Cu, Ag, and Al) were fabricated by room-temperature-molding method and vacuum-warm-compaction method, respectively. X-ray diffraction, Positron annihilation spectroscopy, and density test were utilized to characterize these as-prepared nanocrystalline specimens. The thermal stability and micro-void distribution of the as-prepared nanocrystalline metals were compared and discussed in detail. The experimental results show that the increasing of density is unremarkable while the microstrain reduces during warm-compaction process. The nanocrystalline nonferrous metals prepared by VWC have better thermal stability. Positron annihilation spectroscopy analysis indicates that, compared with the specimens prepared by RM, the average size of micro-void and proportion of single vacancy is a little larger in nanocrystalline copper fabricated by VWC.
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Authors: Antonio Hernando, P. Crespo, M.S. Flores, L. Del Bianco, F. Briones
447
Authors: H. Tanimoto, N. Yagi, H. Mizubayashi
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Authors: J.A. Eastman, M.R. Fitzsimmons, A.C. Lawson, R.A Robinson, L.J. Thompson, J. Satti
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Authors: Johannes Mueller, Karsten Durst, Dorothea Amberger, Matthias Göken
Abstract: The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.
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Authors: J.M. Tao, Xin Kun Zhu, P.Z. Wong, Ron O. Scattergood, Carl C. Koch
Abstract: Shear punch test (SPT) has been used to study the mechanical properties of Cu, Cu–10 wt.% Zn, Cu–20 wt.% Zn and Cu–30 wt.% Zn after ball milling with an average grain size in the range of 33-12nm. The strain rate sensitivity (SRS) and physical activation volume have been determined. The magnitude observed for these characteristic deformation parameters is very different from their course-grained (cg) counterpart. This suggests that the thermally activated process in nanocrystalline (nc) metal/alloys is different from the conventional forest dislocation cutting mechanism. The stacking fault energy (SFE) of Cu-Zn alloys decreased with the adding of Zn, and deformation twins are anticipated to introduce into the nc Cu-Zn alloys during process of ball milling. Dislocations could accumulate along the TBs and carry the plastic strain, so the ductility of nc Cu-Zn alloys could be improved.
373
Authors: Carl C. Koch, Khaled M. Youssef, Ron O. Scattergood
Abstract: This paper reviews a method, “in situ consolidation ball milling” that provides artifactfree bulk nanocrystalline samples for several ductile metals such as Zn, Al and Al alloys, and Cu and Cu alloys. The preparation method is described in this paper and examples of the mechanical behavior of nanocrystalline materials made by this technique are given. It is found that in such artifact-free metals, combinations of both high strength and good ductility are possible.
15
Authors: Agnieszka Daniszewska, Witold Łojkowski, Hans Jorg Fecht, Krzysztof Jan Kurzydlowski, Urszula Narkiewicz, Gennady A. Salishchev, Michael Zehetbauer, Mariusz Kulczyk, Małgorzata Chmielecka, Dmytro Kuzmenko
Abstract: Current and prospective trends in application of metallic nanomaterials have been studied. The study has been conducted within the Nanoroad SME European project – as the first step for a roadmap for industrial application of nanomaterials. The web page of the project is http://www.nanoroad.net/. The present report presents an analysis of patents, papers, national and European projects in the field of nano-metals, and also an analysis of the present state of research and expected trends in this domain. Based on the performed analysis a data base of nanomaterials has been developed as well as roadmaps with expected time to applications. It can be found under http://bourgogne.arist.tm.fr/nanoroadsme/home/. The roadmap is mainly addressed to SMEs to help them to decide about applications or production of nanomaterials.
345
Authors: Deng Pan, S. Kuwano, T. Fujita, M. W. Chen
Abstract: Ultra-large compressive plasticity at room temperature has recently been observed in electrodeposited nanocrystalline nickel (nc-Ni) under micro-scale compression (Pan, Kuwano, Fujita and Chen: Nano Lett. Vol. 7 (2007), p. 2108). With aid of a TEM sample preparation technique employing focused ion beam (FIB), TEM observations on deformed nc-Ni evidenced deformation-induced microstructural evolution of nc-Ni at a variety of strain levels: Whilst the deformation increases, substantial grain growth is uncovered in the nc-Ni. No apparent ex situ evidence of intragranular dislocation activities is found in the deformed sample. As thermal diffusion plays an insignificant role in the deformation in nc-Ni at room temperature (~0.17Tm), this premium plasticity is achieved in accommodation with the grain-boundary-mediated deformation, with assistance of extensive grain growth that is mainly driven by high stresses at steady plastic flow.
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