1991 Fiscal Year Final Research Report Summary
Competing processes of phase separation and disordering during first order transitions in Cu-based alloys
| Project/Area Number |
02650468
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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)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Cupper alloys / Order-disorder transformation / Phase decomposition / Annealing process / Free energy / First order transition / Antiphase boundary |
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| Research Abstract |
Annealing behaviors of Cu based alloys which includes first order transitions have been investigated with special reference of competing processes of phase separation and order-disordering. The following results were obtained.
1. The annealing processes in an L1_1, ordered Cu-39 at%Pt alloy are quite different from each other, depending upon whether the annealing temperature is higher than a certain temperature or not. This phenomenon exhibits that there is a metastable transition line of order-disorder in the area of(L1_1+Al)of the equilibrium phase diagram.
2. In a Cu-25 at%Pt alloy, the transition from L1_<2-S> to L1_<22> proceeds by annihilation of periodic antiphase boundaries of hairpin shape. The hairpin shaped antiphase boundaries(APB)are formed by touching of adjacent perodic APB, or through an aid of thermal APB.
3. Applying the time-dependent Landau-Gintzburg expansion to the kinetic equation, we performed computer-simulation for the annihilation process of periodic APB. The simulation with proper energy-parameters reproduced successfully the annihilation process observed experimentally.
4. In Cu-Ni-Sn alloys with higher concentration of Ni, spinodal decomposition proceeds faster. From the experimental X-ray side bands, the wave-length, amplitude and profile of the composition waves in the alloys have been examined in order to clarify the decomposition processes. The as-quenched alloys show no order-lattice diffraction spots in their diffraction patterns, but after a short annealing, diffuse scatterings for D0_<22> appear. By successive annealing, the scatterings are intensified in alloys with a lower Ni concentration, but they alter to those for L1_2 in higher Ni alloys.
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