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Tsuru, Tomohito; Aoyagi, Yoshiteru*; Shimokawa, Tomotsugu*; Yamaguchi, Masatake; Itakura, Mitsuhiro; Kaburaki, Hideo; Kaji, Yoshiyuki; Chrzan, D. C.*
no journal, ,
Magnesium alloys, one of the lightest metal alloys among metals in practical use, have great potential for next generation of structural materials. Ultrafine-grained metals have been desired to improve strength without allowing. However these materials have crucial disadvantages in practical use in that the elongation-to-failure is relatively low due to the strong anisotropy in plastic deformation of the hexagonal crystal. In this study we investigate the origin of plastic anisotropy caused by crystal structure and microstructure by computational approach.
Ishiyama, Shintaro
no journal, ,
In situ vacuum vaporization and N
ionplanting techniques were applied to improve thermostability of Li target in BNCT, and achieved improvement in high temperature thermaostabolity.
Oka, Hiroshi; Tanno, Takashi; Otsuka, Satoshi; Yano, Yasuhide; Kaito, Takeji; Onuma, Masato*
no journal, ,
Microstructural changes of 9Cr-ODS steel introduced by thermo-mechanical treatment (hot isostatic press (HIP), hot extrusion, and hot forge) were evaluated. The weight-ratio of residual ferrite phase reduced and the number density of nano-oxide particle decreased after the thermo-mechanical treatment. The change of number density and size of nano-oxide particle would affect the weight-ratio of residual ferrite phase because the formation of the residual ferrite phase is led by the pin effect of the nano-oxide particle.
Yamaguchi, Masatake; Itakura, Mitsuhiro; Shiga, Motoyuki; Kaburaki, Hideo; Abe, Eiji*
no journal, ,
no abstracts in English
Kim, Jae-Hwan; Iwakiri, Hirotomo*; Nakamichi, Masaru
no journal, ,
no abstracts in English
M
on hydrogen absorption processMachida, Akihiko; Higuchi, Kensuke*; Watanuki, Tetsu; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
no journal, ,
no abstracts in English
-ironAbe, Yosuke; Sato, Yuki*; Tsuru, Tomohito; Hashimoto, Naoyuki*; Onuki, Somei*
no journal, ,
Temperature dependence of the number density of interstitial clusters was studied for -iron under electron irradiation using a high-voltage electron microscope, and investigated its relation with the one-dimensional (1D) migration behavior. The results show that the number density of interstitial clusters decreases with increasing temperature, and has a positive correlation with the trapping concentration evaluated through the analysis using the 1D migration distances. A rate theory model, in which the migration, coalescence and annihilation processes caused by the 1D migration of interstitial clusters was formulated in this study, clarified that the trapping and de-trapping of interstitial clusters need to be taken into account to understand the nucleation and growth processes of interstitial clusters under electron irradiation.
Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito
no journal, ,
The conversion of polymer precursor, polycarbosilane (PCS) into polymer derived silicon carbide (SiC) by pyrolysis is accompanied by evolution of decomposed gas and volume shrinkage/expansion of PCS. It has been known thermally cured PCS powder is monotonically shrank, however, electron-beam cured PCS powder is expanded at the pyrolysis temperature of around 723 K. We aimed at clarifying why volume of PCS film is expanded by characterizing pyrolyzed powders cured by those methods by measuring the weight change, density and nitrogen isotherm. From the curve of weight decrease during the pyrolysis, it was observed thermally cured PCS evolved larger amount of gases in the temperature range from 673 to 923 K. In the same temperature range, larger total volume of pores formed in pyrolyzed powders was observed for thermally cured PCS powder. It indicates PCS powders were swelled when decomposed gases were evolved. In particular, for electron-beam cured powders, it was observed increase of total pore volume at 723 K even though hardly gases were evolved and the conversion took place, which attributed volume expansion of the PCS powder without shrinkage usually accompanied by the conversion.
Endo, Naruki*; Saito, Hiroyuki; Machida, Akihiko
no journal, ,
no abstracts in English
Itakura, Mitsuhiro; Kaburaki, Hideo; Yamaguchi, Masatake
no journal, ,
Irradiation hardening of nuclear materials are caused by lattice defects which hinder the motion of dislocations and thus suppress plastic deformations. To understand and model the irradiation hardening, the precise knowledge about the dislocation motion inside the material is indispensable. In BCC metals such as iron, the mobility of dislocations is determined by the atomic structure of the dislocation core and thus quantum mechanical calculation is required to estimate the mobility of dislocations. We have devised a new method to calculate the dislocation properties combining linear elasticity theory and quantum mechanical calculations, and also developed a new method to control and investigate the two-dimensional motion of dislocation in the simulation. This work opened a way for the quantitative simulations of irradiation hardening.