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Miyazawa, Takeshi; Tanno, Takashi; Imagawa, Yuya; Hashidate, Ryuta; Yano, Yasuhide; Otsuka, Satoshi; Kaito, Takeji; Mitsuhara, Masatoshi*; Nakashima, Hideharu*; Onuma, Masato*; et al.
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no abstracts in English
Suzudo, Tomoaki; Ebihara, Kenichi; Tsuru, Tomohito; Mori, Hideki*
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BCC metals are used in various applications as structural materials, but they are known to become brittle in the low temperature range and their brittleness is accelerated by impurities such as hydrogen. It is thus desirable to model the phenomenon and predict it appropriately, but the mechanism is complicated and modeling is not easy. The authors have previously simulated penny-shaped cracks using the machine-learning empirical potential of Fe and found that crack growth on {110} planes is suppressed by dislocation emission, which is consistent with the experimental facts that no cracks are observed along this plane. In this study, we report a more detailed analysis of dislocation emission.
-Ti with deformation textureYoshida, Haruki*; Adachi, Nozomu*; Morooka, Satoshi; Xu, P. G.; Harjo, S.; Todaka, Yoshikazu*
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Ito, Yuto*; Egusa, Daisuke*; Yamaguchi, Masatake; Abe, Eiji*
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Takanashi, Koki
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Tsuru, Tomohito; Lobzenko, I.
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In highly-concentrated alloys such as high-entropy alloys (HEAs) and gum metals, excellent mechanical properties that achieve strength with sufficient ductility and toughness have been discovered. Recent studies have confirmed that HEA with BCC structure exhibits unique mechanical behavior that cannot be explained by solid solution strengthening of highly-concentrated alloys. In this study, the origin of the unique mechanical properties is investigated using first-principles calculations, a linear tension model, and a machine learning potential based on the dataset from first-principles calculations. Our calculations reveal that the relatively high strength and peculiar slip anisotropy observed in TiZrNbHfTa are due to intrinsic properties of dislocation motion caused by high concentrations of group IV elements. The effect of these features on dislocation motion is reproduced using a line tension model of dislocations, which qualitatively shows that highly-fluctuated potential energy surfaces lead to heterogeneous kink formation and an increase in the yield stress.
Wakai, Eiichi; Noto, Hiroyuki*; Shibayama, Tamaki*; Nakagawa, Yuki*; Ishida, Taku*; Makimura, Shunsuke*; Wakui, Takashi; Furuya, Kazuyuki*; Ando, Masami*
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In the fields of energy, nuclear power, high-energy accelerator target systems, nuclear fusion, and biology, radiation causes degradation of materials and equipment, and thus it is expected to create new materials with high durability and superior functionality. In this study, for Fe-, Ti-, and W-based high-entropy alloys (HEA) composed of low activation elements (Ni and Co free), Fe-based alloys were prepared by radio frequency melting, Ti-based alloys by cold crucible levitation melting, and W-based alloys by arc melting using metal powders. These materials were tested by X-ray diffraction, microstructural observation, hardness measurement, magnetic measurement, electrical resistivity measurement, scanning transmission electron microscope STEM (or TEM, SEM) and energy dispersive X-ray spectroscopy, ultrasonic measurement, and hot isostatic pressing (HIP) method. These HEAs were found to be much harder than normal alloys, and in Fe-based HEAs, the magnetic properties and related microstructural analysis showed that they have interesting characteristics such as micro magnetic domain structures. In particular, for Fe- and W-based HEAs, the changes in crystal structure, orientation, and internal microstructure caused by HIP treatment and the accompanying effects of high temperature and pressure have been found to have a significant effect on magnetic properties and material strength properties.
Gong, W.; Harjo, S.; Kawasaki, Takuro; Mao, W.; Aizawa, Kazuya
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Gong, W.; Zheng, R.*; Harjo, S.; Kawasaki, Takuro; Tsuji, Nobuhiro*
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Yano, Yasuhide; Tanno, Takashi; Otsuka, Satoshi; Mitsuhara, Masatoshi*; Nakashima, Hideharu*; Toyama, Takeshi*; Onuma, Masato*
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no abstracts in English
Suzuki, Kazuya; Takanashi, Koki
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High-entropy alloys (HEAs) have attracted much attention due to their excellent mechanical properties, heat resistance, corrosion resistance, and irradiation resistance, but most of the research has been directed toward their application as structural materials. HEA has the potential to exhibit excellent electromagnetic functions that are not found in conventional alloys. In particular, new applications of HEA materials are expected to be developed by applying the fabrication method of nanoscale highly structurally controlled nano-layered thin films, which is a specialty of the spintronics field. In this study, we focus on FeNiCoCuPd alloys, which exhibit Curie temperatures higher than room temperature, and report on the fabrication and basic properties of these thin films.
Saito, Toshiki*; Yu, H.*; Inoue, Koji*; Zimo, G.*; Kondo, Sosuke*; Kasada, Ryuta*; Nagai, Yasuyoshi*; Oba, Yojiro; Hiroi, Kosuke
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no abstracts in English