Papers by Author: Satoshi Semboshi

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Authors: Satoshi Semboshi, Hiroshi Numakura, Wei Lin Gao, Hisashi Suda, Akira Sugawara
Abstract: Aging solution-treated Cu-Ti alloys in a hydrogen atmosphere significantly improved their electrical conductivity without degradation of the mechanical strength, compared to conventionally aged alloys. In this study, the influence of prior deformation on the mechanical and electrical properties of Cu-4.2 at.% Ti alloys aged in a hydrogen atmosphere was examined. The Vickers hardness of the solution-treated specimen increased from 127 kgf/mm2 to 265 kgf/mm2 by aging at 673 K for 180 h in a hydrogen atmosphere of 0.8 MPa, while that of the deformed specimen achieved a maximum of approximately 280 kgf/mm2 by aging for 100 h in the same atmosphere. Prior deformation resulted in a more rapid increase in conductivity during aging than that without deformation. The conductivity at the peak-hardness of the deformed specimen was 22% IACS (International Annealed Copper Standard), which exceeded that for the solution-treated specimen. Thus, prior deformation assisted in a significant improvement of the mechanical and electrical properties during aging in a hydrogen atmosphere.
Authors: Satoshi Semboshi, Naoya Masahashi, Toyohiko J. Konno, Shuji Hanada
Authors: W.-Y. Kim, Y. Sato, Satoshi Semboshi, Shuji Hanada, Hiroyuki Kokawa
Authors: Mika Kano, Takashi Ito, Motoaki Matsuo, Shigeyuki Takagi, Satoshi Semboshi, Shinichi Orimo
Abstract: It Has Been Reported that the Metal Hydride, Ymn2hy (y ≤ 4.5), Wherein the Hydrogen Atoms Are Located into the Interstitial Sites, Transformed into a Complex Hydride, YMn2H6, Containing Complex Anions, [MnH6]5-. We Investigated the Possibility of Synthesizing the Complex Hydride, Y(Mn1-xFex)2H6 (x ≤ 0.3), where Mn Atoms Were Partially Substituted by Fe. As a Result, the Transformation into the Complex Hydride, Y(Mn1-Xfex)2H6, Was Successfully Realized for x ≤ 0.10 upon the Hydrogenation of the Metal Hydride, Y(Mn1-xFex)2Hy (y = 4.4 and 4.5), under 50 Mpa H2, much Lower than the Previously Reported Value of 1 GPa. Our Structural Investigation Suggested that the Fe Substitution in Y(Mn1-xFex)2H6 (x ≤ 0.10) Resulted in the Form of Complex Anions, I.e., [MnH6]5- Were Partially Substituted by [FeH6]4-.
Authors: Ken Ichi Nishikawa, Satoshi Semboshi, Toyohiko J. Konno
Abstract: Environmentally friendly Cu-based alloys with high strength and low electrical resistivity have been much sought in order to replace deleterious Cu-Be alloys for electrical applications. As one of the candidate systems, we have examined age-hardening behaviors of Cu-Mg alloys by using transmission electron microscopy (TEM). Cu-2.26wt.%Mg alloys were solution-treated and annealed at 723K, and their structural changes have been investigated. The Vickers hardness measurements showed that they aged-harden gradually. Our TEM observations showed that annealing for 6h brings about precipitation of numerous needle-like particles of 10 nm in length. The diffraction studies indicated these precipitates consist of the Cu2Mg phase with {111}Cu habit planes. When annealed for 96h, these precipitates become semi-coherent, which was manifested by moiré fringes; while maintaining the orientation relationship of (111)Cu//(111)Cu2Mg, [110]Cu//[110]Cu2Mg.
Authors: Rimi Nishio, Toyohiko J. Konno, Satoshi Semboshi
Abstract: Phase separation behaviors of a quenched Cu-3.0at%Ti alloy, as well as crystallographic structures of Cu-20.7at%Ti alloy have been studied using transmission electron microscopy. The furnacecooled Cu-20.7at%Ti alloy are composed of a-Cu4Ti (Ni4Mo-type) and b-Cu4Ti (Au4Zr-type) with the orientation relationship of (011)a//(110)b, [100]a//[001]b. As-quenched Cu-3.0at%Ti alloy showed a modulated structure with the modulation length of about 4 nm. When aged at 723K for 8 hr, the a-Cu4Ti phase emerges within the modulated or tweed-like microstructure. Prolonged aging results in the growth of the a-Cu4Ti particles and the loss of coherency. It is likely that asquenched Cu-3.0at%Ti alloy decomposes spinodally at 723K, followed by polymorphous ordering; though the present study did not exclude, as an alternative path, a decomposition mechanism based on the catastrophic nucleation.
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