Formation mechanism of ordering waves and ordering process in CuPt alloys
Project/Area Number 
62550478

Research Category 
GrantinAid for General Scientific Research (C)

Allocation Type  Singleyear Grants 
Research Field 
Physical properties of metals

Research Institution  Kyushu University 
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)

CoInvestigator(Kenkyūbuntansha) 
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)

Project Period (FY) 
1987 – 1989

Project Status 
Completed (Fiscal Year 1989)

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)

Keywords  Cupper platinum alloy / Orderdisorder 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 
Research Abstract 
Orderdisorder processes in CuPt 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 onedimensional pairwise interactions which have frustration. The energy reduction stabilizes the states of SRO and L1_<2s>. 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 Cu40 at%Pt alloy was investigated by Xray 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 A1L1_1 transformation. The process from A1 to (A1+L1_1) was also discussed.

Report
(4 results)
Research Products
(8 results)