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Iwamoto, Yosuke; Wakai, Eiichi; Nakagawa, Yuki*; Shibayama, Tamaki*
no journal, ,
In order to develop a new non-destructive inspection technique to accurately measure defects inside materials in radiation fields such as nuclear power plants, accelerators, and aerospace, we have measured the time evolution of electrical resistivity of copper, aluminum, and niobium metal wires and silicon plates by irradiating a pulsed laser beam (20 Hz) at Hokkaido University. From the obtained increase in electrical resistivity, the number of atomic vacancies and Frenkel pairs (FPs) of interstitial atoms and the dislocation density of the formed FPs were estimated, assuming that the atoms were ejected by the laser due to electronic excitation. From this experiment, it was estimated that for metals, the amount of defects formed inside the material increased with the increase in the irradiation dose. On the other hand, for silicon, the electrical resistivity was found to decrease due to the electronic transition to the valence band caused by laser irradiation.
Toyota, Kodai; Wakai, Eiichi; Onizawa, Takashi; Shibayama, Tamaki*; Nakagawa, Yuki*
no journal, ,
no abstracts in English
Wakai, Eiichi; Iwamoto, Yosuke; Shibayama, Tamaki*; Sato, Koichi*; Toyota, Kodai; Onizawa, Takashi; Wakui, Takashi; Ishida, Taku*; Makimura, Shunsuke*; Nakagawa, Yuki*; et al.
no journal, ,
In the fields of accelerator target systems, nuclear power, aerospace, etc., radiation degradation of structural materials and equipment occurs, and therefore, the development of materials with high durability and excellent functions is expected. In order to create innovative materials that can be used in radiation fields, we are developing a new non-destructive inspection technique that can accurately measure the internal defects of various materials in radiation fields. As an innovative material, high-entropy alloys (HEA) are known for their high strength and ductility, and are expected to be used in various applications. In this talk, we will report on the construction of a measurement principle that enables multi-simultaneous measurements even in radiation fields, the status of HEA prototypes, and the status and progress of irradiation analysis of metals and other materials.
Wakai, Eiichi; Noto, Hiroyuki*; Shibayama, Tamaki*; Iwamoto, Yosuke; Sato, Koichi*; Yano, Yukihiro*; Yoshikawa, Maya*; Nakagawa, Yuki*; Toyota, Kodai; Onizawa, Takashi
no journal, ,
In this study, we attempted to fabricate Fe-based and W-based Fe-HEA and W-HEA, both of which have been studied extensively in recent years to enhance the durability of equipment used in high-energy beam irradiation environments. For Fe-based HEAs, Fe-Mn-Cr-V-Al-C alloys were melted and casted, and then subjected to homogenization heat treatment (homogenization heat treatment (1150
C for 2h)). After homogenization heat treatment, a 3-point bending test was performed at room temperature. The homogenization heat treatment resulted in an increase in ductility in the 3-point bending test and a decrease in elastic modulus based on ultrasonic velocity measurements. XRD measurements of this material after heat treatment (800C for 10 min and Water Quenched) showed that it has a BCC structure and a Vickers hardness that exceeds that of pure W. On the other hand, in the preparation of W-based HEA material (W-Fe-Si-V-Cr alloy), an arc melting method using powder was attempted, and it was found that an almost homogeneous crystallized alloy could be produced.
Wakai, Eiichi; Noto, Hiroyuki*; Shibayama, Tamaki*; Nakagawa, Yuki*; Ishida, Taku*; Makimura, Shunsuke*; Wakui, Takashi; Furuya, Kazuyuki*; Ando, Masami*
no journal, ,
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.