1999 Fiscal Year Final Research Report Summary
Development of tungsten alloys for high-heat-flux components application
| Project/Area Number |
09558061
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Nuclear fusion studies
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
KURISHITA Hiroaki IMR, Tohoku Univ., Assoc. Prof., 金属材料研究所, 助教授 (50112298)
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| Co-Investigator(Kenkyū-buntansha) |
TOKIDA Tomohiro Tokyo Tungsten Co, Ltd., Researcher, 研究開発部, 研究員
YUBUTA Kunio IMR, Tohoku Univ., Research Assoc., 金属材料研究所, 助手 (00302208)
HIRAOKA Yutaka Okayama Science Univ., Prof., 理学部, 教授 (70228774)
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| Project Period (FY) |
1997 – 1999
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| Keywords | tungsten / transition metal carbide / mechanical alloying / low temperature embrittlement / recrystallization embrittlement / radiation embrittlement / radiation induced ductilization / precipitates |
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| Research Abstract |
Tungsten is superior to other materials in physical and mechanical properties for use as high heat flux components infusion reactors. Key issue of the metal is to improve three embrittlement, I.e., low temperature embrittlement, recrystallization embrittlement and radiation embrittlement. In order to achieve simultaneous and significant improvements in those embrittlement, microstructures with very fine grains and dispersed particles of transition metal carbides (TMC) at grain boundaries may be most effective. Thus, to obtain such microstructures the mechanical alloying and hot isostatic pressing methods were applied to mixed powders of tungsten and TMC including TiC and HfC (group IV th) and TaC and NbC (group V th). Tungsten alloys thus prepared were subjected to impact 3-point bending tests to evaluate low temperature toughness, vacuum heating up to 2200 ℃ to evaluate recrystallization temperature and fast neutron irradiation experiments followed by PIE to evaluate radiation embrittlement. Microstructural observations were also made. It was found that among the prepared alloys, TiC added ones exhibited the most improved properties ; the alloys with 0.2wt% TiC addition showed much lower ductile-to-brittle transition temperature (by above 100 ℃) and much higher recrystallization temperature (by approximately 600 ℃) than commercially available pure tungsten and its alloys. It was also found that for achieving the improvement in radiation embrittlement which is the most crucial issue, the suppression of radiation hardening cannot be a solution, but active use of microstructural changes taking place during irradiation, such as radiation-induced or radiation-enhanced precipitation, to strengthen the weakest points in microstructures, providing the alloy composition that does not permit the precipitation of very brittle WィイD22ィエD2C.
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