| Project/Area Number |
62550478
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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 |
Physical properties of metals
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| Research Institution | Kyushu University |
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Principal Investigator |
KUWANO Noriyuki Kyushu University, Graduate School of Engineering Sciences, Associate Professor, 総合理工学研究科, 助教授 (50038022)
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| Co-Investigator(Kenkyū-buntansha) |
ITAKURA Masaru Kyushu University, Graduate School of Engineering Sciences, Research Associate, 総合理工学研究科, 助手 (20203078)
MATSUMURA Syo Kyushu University, Graduate School of Engineering Sciences, Research Associate, 総合理工学研究科, 助手 (60150520)
OKI Kensuke Kyushu University, Graduate School of Engineering Sciences, Professor, 総合理工学研究科, 教授 (70037860)
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| Project Period (FY) |
1987 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1989: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1988: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1987: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Cupper platinum alloy / Order-disorder transformation / Free energy / Kinetic equation / Short range order / Phase decomposition / Ordering wave / First order transition / 規則・不規則転移 / 等温焼鈍過程 / 規則化過程 / 自由エネルギー / 規則合金 / フィールドイオン顕微鏡 / 電子顕微鏡 / 規則ドメイン |
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| Research Abstract |
Order-disorder processes in Cu-Pt alloys were studied in order to clarify the mechanism of the first order transformation. The following results were obtained.
1. The kinetic equation was established for simulation of ordering process from short range ordered state (SRO) to L1_2 or to L1_<-s> in a Cu_3Pt alloy. In the formulation, the density of free energy is expressed by a Landau expansion with the local degree of order S_r. Surface energy is represented in terms of S_r, S_r^2 and |S_r| so that a low antiphase energy may be taken into account. The magnitude of energy reduction due to antiphase correlation is assumed to be proportional to the amplitude of Fourier transformed S_r. The proportionality constant can be obtained by Fourier transformation of one-dimensional pairwise interactions which have frustration. The energy reduction stabilizes the states of SRO and L1_<2-s>. The state of SRO and the ordering processes can be produced by numerical calculation of the kinetic equation which consists of the above terms plus thermal fluctuation.
2. The process of phase decomposition from L1_1 into (A1+L1_1) in Cu-40 at%Pt alloy was investigated by X-ray diffraction and electron microscopy. It was found that, if the annealing temperature T_a is higher than a certain one T_m, the alloy is disordered almost completely to A1, followed by precipitation of L1_1. When T_a<T_m, the phase decomposition proceeds by precipitation of A1 in L1_1. The temperature dependence of annealing process is explained thermodynamically by assuming that T_m corresponds to the critical temperature of the alloy for A1-L1_1 transformation. The process from A1 to (A1+L1_1) was also discussed.
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