| Project/Area Number |
01550077
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
材料力学
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| Research Institution | Sophia University |
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Principal Investigator |
NOZUE Akira Sophia University Faculty of Science and Technology Associate Professor, 理工学部, 助教授 (80146802)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Hiroshi Sophia University Faculty of Science and Technology Research Associate, 理工学部, 助手 (30154579)
SHIRASUNA Yosio Sophia University Faculty of Science and Technology Research Associate, 理工学部, 助手 (90053652)
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1990: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1989: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Ti alloy / Hydrogen embrittlement / Fracture toughness / Heat treatment / 破壊靱性 / ゾ-ンシ-ルディング |
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| Research Abstract |
The present study was carried out for the past two years in order to reduce the susceptibility of hydrogen embrittlement and to enhance the fracture toughness with a special process using hydrogen for beta Ti alloys such as Ti-3Cr-3Sn-3Al alloy.
The beta Ti alloy of the good cold formability exhibited the extremely high susceptibility of hydrogen embrittlement in comparison with Ti-6Al-4V alloy of a alpha-beta type used the most widely. This susceptibility of the beta Ti alloy was found to be reduced by decreasing alpha precipitation. However, the strength of the present alloy is reduced due to a decrease in the volume fraction of alpha precipitation. Hence a special heat treatment process has been developed to reduce the susceptibility. For this reduction it is found to be necessary to form free precipitation zones almost around bet a grain boundaries because of their extremely high fracture resistance.
That is, this process is as follows ; the specimens were solution-treated at relatively high 950^ﾟC, aged at 510^ﾟC for 4h and then aged at 440^ﾟC for 3h.
As described above, hydrogen is not a good element for the fracture toughness of the Ti alloys. The second work is to enhance the fracture toughness with a special process using hydrogen. The zone shielding method used for composites and ceramics has been applied to the present alloy. Hydrogen was occluded for specimens with a cathode charging method and then only hydrogen solid-dissolved at the beta matrix was evoluted with a relatively low heating process in a vacuum while hydrides existed at the precipitation alpha. In these specimens microcrack toughening at the precipitation alpha occurred during loading. As a result, about 20% level of the fracture toughness was increased.
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