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Fang, W.*; Liu, C.*; Zhang, J.*; Xu, P. G.; Peng, T.*; Liu, B.*; Morooka, Satoshi; Yin, F.*
Scripta Materialia, p.116046_1 - 116046_6, 2024/05
Ikeda, Yoichi*; Umemoto, Yoshihiko*; Matsumura, Daiju; Tsuji, Takuya; Hashimoto, Yuki*; Kitazawa, Takafumi*; Fujita, Masaki*
Materials Transactions, 64(9), p.2254 - 2260, 2023/09
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Yang, J.*; Ren, W.*; Zhao, X.*; Kikuchi, Tatsuya*; Miao, P.*; Nakajima, Kenji; Li, B.*; Zhang, Z.*
Journal of Materials Science & Technology, 99, p.55 - 60, 2022/02
Times Cited Count：6 Percentile：45.20(Materials Science, Multidisciplinary)High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lattices, differing from traditional alloys. Here, we investigate magnetic and thermal transport properties of the prototype face-centered-cubic high-entropy alloy CrMnFeCoNi by combining physical properties measurements and neutron scattering. Direct-current (dc) and alternating-current (ac) magnetizations measurements indicate a mictomagnetic behavior with coexisting antiferromagnetic and ferromagnetic interactions in the entire temperature region and three anomalies are found at about 80, 50, and 20 K, which are related to the paramagnetic to antiferromagnetic transition, the antiferromagnetic to ferromagnetic transition, and the spin freezing, respectively. The electrical and thermal conductivities are significantly reduced compared to Ni and the temperature dependence of lattice thermal conductivity exhibits a glass-like plateau. Inelastic neutron scattering measurements suggest weak anharmonicity so that the thermal transport is expected to be dominated by the defect scattering.
Naeem, M.*; Zhou, H.*; He, H.*; Harjo, S.; Kawasaki, Takuro; Lan, S.*; Wu, Z.*; Zhu, Y.*; Wang, X.-L.*
Applied Physics Letters, 119(13), p.131901_1 - 131901_7, 2021/09
Times Cited Count：9 Percentile：63.89(Physics, Applied)Lam, T.-N.*; Lee, S. Y.*; Tsou, N.-T.*; Chou, H.-S.*; Lai, B.-H.*; Chang, Y.-J.*; Feng, R.*; Kawasaki, Takuro; Harjo, S.; Liaw, P. K.*; et al.
Acta Materialia, 201, p.412 - 424, 2020/12
Times Cited Count：34 Percentile：91.29(Materials Science, Multidisciplinary)Lam, T.-N.*; Chou, Y.-S.*; Chang, Y.-J.*; Sui, T.-R.*; Yeh, A.-C.*; Harjo, S.; Lee, S. Y.*; Jain, J.*; Lai, B.-H.*; Huang, E.-W.*
Crystals (Internet), 9(8), p.420_1 - 420_8, 2019/08
Times Cited Count：9 Percentile：66.85(Crystallography)Suzuki, Kazuya; Takanashi, Koki
no journal, ,
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.
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.
Suzuki, Kazuya; Takanashi, Koki
no journal, ,
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 magneto-transport properties of these thin films.
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.
Hashimoto, Naoyuki*; Isobe, Shigehito*; Oka, Hiroshi*; Hayashi, Shigenari*; Ueda, Mikito*; Yamashita, Shinichiro; Itakura, Mitsuhiro; Tsuru, Tomohito
no journal, ,
Owing to the reduced defects, low cost, and high efficiency, the additive manufacturing (AM) technique has attracted increasingly attention and has been applied in high-entropy alloys (HEAs) in recent years. For the purpose of creating new materials which show no radiation damage or prompt recovery of radiation damage, we launched a new program in which additive-manufactured HEAs are target materials and their fundamental properties are under investigation. In this presentation, we reported the some of new test results which are conducted in the program.
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; Shibayama, Tamaki*; Noto, Hiroyuki*; Furuya, Kazuyuki*; Iwamoto, Yosuke; Wakui, Takashi; Makimura, Shunsuke*; Ishida, Taku*; Ando, Masami*; Sato, Koichi*; et al.
no journal, ,
In fields such as nuclear power and high-energy accelerator target systems, radiation causes degradation of materials and equipment, so materials with high durability and excellent functionality are expected to be created. High-entropy alloys (HEA) are expected to have high irradiation resistance and often have high strength and good ductility. In recent years, research and development is underway worldwide for various applications. In this study, Fe- and Ti-based and W-based HEAs composed of low activation elements (free of Ni and Co) were fabricated. These materials were subjected to X-ray diffraction, microstructural observation, hardness, magnetism, electrical resistance, STEM (or TEM, SEM) and EDS, ultrasonic measurements, and hot isostatic pressing (HIP). Ion irradiation, pulsed laser irradiation, and pulsed electron beam irradiation were also performed on some of the samples to investigate their response characteristics. These HEAs were much harder than normal alloys, and the magnetic properties and related microstructural analysis of Fe-based HEAs revealed that they have interesting properties such as micro magnetic domain structures. In particular, for Fe- and W-based HEAs, the changes in crystal structure, orientation, and internal microstructure induced by HIP treatment and the accompanying effects of high temperature and pressure had a significant effect on magnetic properties and material strength properties. Furthermore, the irradiation response properties of Fe-based HEAs have been characterized.
-phase based titanium alloysWakai, Eiichi; Ishida, Taku*; Kano, Sho*; Shibayama, Tamaki*; Sato, Koichi*; Noto, Hiroyuki*; Makimura, Shunsuke*; Furuya, Kazuyuki*; Yabuuchi, Atsushi*; Yoshiie, Toshimasa*; et al.
no journal, ,
Titanium materials have been applied to beam window materials and beam dumps in large accelerator systems because of their low specific gravity, high corrosion resistance, strength, and other advantages. As the beam power becomes higher, further improvement of irradiation resistance is required. We have investigated further the properties of titanium alloys based on the -phase, and it was found that Ti-15-3-3-3 alloys have excellent irradiation resistance when subjected to ion irradiation. In order to investigate the cause of this, microstructures and point defects in this and related materials were evaluated by TEM, positron lifetime measurement, electrical resistivity, and stress-induced changes, among others. In addition, we have recently begun to develop a prototype of a titanium-based high-entropy alloy based on -titanium, which is attracting worldwide attention and is being developed, and have also begun to evaluate the emotional properties of this alloy. We have examined the various properties of this material and found that it has considerably higher strength than conventional iron- and titanium-based materials.
Takanashi, Koki
no journal, ,
First, the vision of JAEA and the research on energy materials at the Advanced Science Research Center in accordance with the JAEA vision will be introduced. Then, the presenter describes his research on the spin-thermoelectric effects in metallic superlattices and high-entropy alloys, and its application to nuclear batteries.
Wakai, Eiichi; Noto, Hiroyuki*; Shibayama, Tamaki*; Iwamoto, Yosuke; Ishida, Taku*; Sato, Koichi*; Yabuuchi, Atsushi*; Yoshiie, Toshimasa*; Takahashi, Toshiharu*; Kobayashi, Yasuhiro*; et al.
no journal, ,
In recent years, it has been reported that high-entropy alloys (HEA) have high strength but good ductility, and they are being researched and developed by cutting-edge research institutions around the world with the aim of finding various applications in progress. In this study, we considered several Fe-based, W-based, and Ti-based HEAs, excluding Co and Ni elements, in order to aim for use in high radiation fields and considering low-activation properties. These materials mainly have a bcc crystal structure and were fabricated using a melting method and their material properties were evaluated. As a result, it was found that Fe-based HEA has properties that exceed the hardness of pure W and has excellent irradiation resistance. In addition, a Ti-based HEA that can be subjected to high-temperature forging and high-temperature rolling has been found, and evaluation of the optimal heat treatment temperature is progressing. The hardness of W-based HEA increased through Hot Isostatic Pressing (HIP) treatment, and it was found to have the world's highest hardness among HEA materials.
Wakai, Eiichi; Shibayama, Tamaki*; Noto, Hiroyuki*; Wakui, Takashi
no journal, ,
In this study, we fabricated a prototype iron-based high-entropy alloy (Fe-Mn-V-Cr-Al-C) composed of low activation elements (free of Ni and Co) by radio frequency melting method and evaluated its basic properties, aiming to apply it to new functional materials for high-energy accelerator target system components, nuclear reactors and fusion reactors. XRD analysis of this material revealed that it has a BCC crystal structure, in which vanadium carbide (VC) is precipitated. This material was found not only to be magnetic, but also to have a fairly small magnetic domain structure. As for the grain size, relatively small grains (about 20-50 
m) were observed despite the homogenization heat treatment at 1150C. With regard to strength properties, the results of Vickers hardness measurements indicated that the alloy was much harder than ordinary iron alloys, slightly exceeding pure tungsten, and elastic wave velocity measurements showed that it was faster than iron-based materials and had a higher elastic modulus than stainless steel.
Yamashita, Shinichiro; Hashimoto, Naoyuki*; Oka, Hiroshi*
no journal, ,
In order to understand irradiation behavior of RA-MEA, CrFeMnNi alloy, up to the range of irradiation dose exceeding 100 dpa and demonstrate the applicability of AM to some of FCC single-phase nuclear materials, ion irradiation testing was performed. The conclusions obtained are as follows: In both microstructures of CrFeMnNi alloy prepared by conventional arc-melting or AM, a dense and fine cavity formed due to ion-irradiation over 200 dpa. However, estimated swellings (
V/V), which were calculated on the assumption that the thickness of all thin film samples is constant in this study, were 0.20% for arc-melted CrFeMnNi alloy and 0.63% for SLMed CrFeMnNi alloy, respectively. In the case of RA-MEAs, regardless of the difference in fabrication method, it was experimentally confirmed that RA-MEAs have high dimensional stability. In both microstructures of 316L after ion-irradiation over 200 dpa, void formation was confirmed. Void size distribution in SLMed 316L was quite different from that in arc-melted 316L, leading to the difference in estimated swellings between SLMed and arc-melted 316Ls; 0.52% (SLM) vs 6.61% (Arc-melting) This can be explained attributing to the difference in initial microstructure. Superior irradiation resistance in RA-MEA and Applicability of AM to nuclear structural materials were successfully confirmed.
Wakai, Eiichi; Noto, Hiroyuki*; Makimura, Shunsuke*; Ishida, Taku*; Furuya, Kazuyuki*; Shibayama, Tamaki*
no journal, ,
Recently, high-entropy alloys have been vigorously researched and developed by research institutes around the world because of their higher strength and ductility than conventional materials due to their atomic mixing ratio and composition. In this study, titanium-based high-entropy alloys (HEAs), TiVCrZrTa, TiVZrTaAl, and TiVCrZrW, were melted by the cold crucible surface melting method and subjected to homogenization heat treatment at 1200C for 5 hours. Mechanical property tests and properties of these HEAs were investigated, and it was found that the TiVCrZrTa HEAs have relatively better hot-rollability and hot-forgeability than other titanium-based HEAs. The Vickers hardness of these titanium-based HEAs was also found to be considerably higher than that of normal titanium alloys.
