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Suzudo, Tomoaki; Nagai, Yasuyoshi*
no journal, ,
In the ferrite phase of stainless steel weld-overlay cladding of reactor pressure vessels, the hardening caused by a phase separation of Fe-Cr systems is reported, and the experiments suggests that the hardening takes place even in the early stage of phase separation. In the current study, we reproduced and thoroughly analyzed this hardening phenomena by exploiting molecular dynamics. We observed that the Cr-rich phase caused by the phase separation is a week obstacle for dislocation motions. In addition, the deviation of Cr-concentration distribution function from the binomial distribution (i.e. V-parameter) and hardness roughly had a linear relationship as observed in experiments.
-ironAbe, Yosuke; Sato, Yuki*; Suzudo, Tomoaki; Tsuru, Tomohito; Hashimoto, Naoyuki*; Onuki, Somei*
no journal, ,
One-dimensional (1D) migration behavior of self-interstitial atom (SIA) loops was studied for specimens of -iron with different purities under electron irradiation using the HVEM at Hokkaido University. As increasing temperature, saturated loop number densities decreased and 1D jump distances became longer, indicating that the total concentration of trapping sites for SIA loops decreases at higher temperatures. According to the developed rate theory model, it was shown that the dependence of the irradiation intensity on the loop number density tends to be weaker with lowering the impurity concentration at room temperature.
Tsukada, Takashi
no journal, ,
no abstracts in English
Takeyama, Akinori; Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito
no journal, ,
In order to prepare crack-free silicon carbide hydrogen separation membrane, how volume shrinkage or expansion of polymer precursor, polycarbosilne (PCS) take places when it is converted into silicon carbide ceramics during pysolysis was investigated. PCS powder cured by electron beam irradiation with several dose of 12,16,18,24 MGy in helium atmosphere was pysolysed at 923 K to convert them into SiC ceramic powder. As the dose was increased, ceramic yield was gradually increased, indicating amount of decomposed gas evolved during pyrolysis was decreased. Density of obtained SiC ceramic powders was decreased with increasing dose. By electron beam irradiation, network structure of PCS was developed and decomposition gas seemed to be easily accumulated in the network structure. It follows that PCS powder swelled as decomposition gas was accumulated and swelling was lowered density of SiC ceramic powders. Furthermore, surface area of SiC ceramic powder was increased from 0 m
/g for 12 MGy to 0.6 m/g for 24 MGy by swelling. Consequently, swelling suppressed volume shrinkage of PCS powder during pyrolysis.
Yamaguchi, Masatake; Itakura, Mitsuhiro; Kaburaki, Hideo; Tsuru, Tomohito
no journal, ,
no abstracts in English
FeH
at high pressures and high temperaturesSaito, Hiroyuki; Takagi, Shigeyuki*; Matsuo, Motoaki*; Iijima, Yuki*; Endo, Naruki; Aoki, Katsutoshi; Orimo, Shinichi*
no journal, ,
no abstracts in English
Yamaguchi, Masatake; Kameda, Jun*; Ebihara, Kenichi; Itakura, Mitsuhiro; Kaburaki, Hideo
no journal, ,
no abstracts in English
Yamaguchi, Masatake; Itakura, Mitsuhiro; Shiga, Motoyuki; Kaburaki, Hideo; Abe, Eiji*
no journal, ,
no abstracts in English
Shi, S.*; Ono, Naoko*; Ukai, Shigeharu*; Hayashi, Shigenari*; Togo, Koichi*; Fukumoto, Kenichi*; Abe, Yosuke
no journal, ,
Bubble dispersion strengthened (BDS) copper was synthesized by using the dissociated gases of the poly methyl methacrylate (PMMA) during Spark Plasma Sintering (SPS). By in-situ TEM observation under tensile loading, we analyzed a detachment angle of the dislocation from the bubble, and evaluated the pinning force of bubble for the moving dislocations. TEM observation showed homogeneously dispersed bubbles in Cu-5vol
PMMA and average bubble size was about 10 nm in diameter. It was analyzed that dispersed bubbles can strengthen copper with an angle 79
at dislocation detached from bubbles, which was consistent with the interaction angle 74 estimated by Vickers hardness measurement of the same specimen.