| Project/Area Number |
08650825
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Structural/Functional materials
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| Research Institution | Okayama University of Science |
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Principal Investigator |
SUKEDAI Eiichi Okayama University of Science, Department of Mechanical Engineering, Professor, 工学部, 教授 (00090217)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1997: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1996: ¥800,000 (Direct Cost: ¥800,000)
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| Keywords | beta-Ti allovs. / omega-phase transformation. / HREM. / In-situ observation. / aging under stress. / hvdrostatic pressure. / critical pressure. / initial structure of omega-phase crystals / ω相変態 / 静水圧負荷 / 高分解電子顕微鏡 / 原子半径差 / 格子歪 |
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| Research Abstract |
In beta-Ti alloys, omega-phase transformations are occurred due to three ways, that is, quenching from temperature above beta-transus, aging and stressing. omega-phase crystals make beta-Ti alloys harder and more brittle. Recently, it was found that omega-phase crystals become nucleation sites of alpha-transformation by means of longer-time aging or higher temperature aging. beta-Ti alloys including fine alpha-phase particles, (beta+alpha) duplex Ti alloys are stronger and more ductile. The purpose of this research is to develop new methods to make higher density of omega-phase crystals in beta-Ti alloys as nucleation-siters of alpha-phase particles and to clarify the omega-phase transformation mechanism. A high resolution erectron microscope method was used to clarify the beta to omega transformation behaviors at atomic level. The results obtained are as follows :
(1). As-quenched omega-phase crystals were unstable, and almost of them disappeared during the heating.
(2). Aged omega-phase crystals grew from the remained as-quenched omega-phase crystals as nucleation sites.
(3). A tensile stress during the aging and hydrostatic pressurizing were effective to promote high density aged omega-phase crystals.
(4). It was recognized that the critical hydrostatic pressure to make omega-phase crystals was between 0.5 and 0.7 GPa.
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