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Atomistic Mechanisms of Phase Transformations in Metals and Alloys

金属和合金中相变的原子机制

基本信息

批准号：
01302054
负责人：
KOIWA Masahiro
金额：
$ 5.89万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Co-operative Research (A)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

Mechanisms of Phase transformations in various material have been studied with a variety of advanced experimental techniques. Some examples of the results obtained in this Cooperative Research are briefly described below.1. Structural and lattice dynamical investigations have been performed on the intermetallic compounds : NiAl, ZrNb and FePd, by neutran diffraction and scattering experiments. Structural fluctuation in mesoscopic scale is found near the temperature of transformation from the bcc- to the martensitic phase. This fluctuation is termed the heterophase fluctuation, which is believed to be characteristic of the martensitic transformation.2. A combination of the Imaging Plate and a synchrotron-radiation source has been shown to be powerful for the observation of changes in the two-dimensional intensity distribution of diffuse scattering. X-ray diffuse scattering from an AgZn single crystal having the B2-type structure were observed successively during the structural transition from the beta' phase to the zata phase. It has been shown in a series of patterns taken at a time interval of 600s that a diffuse intensity sheet extending parallel to the (111) relplane gradually loses its intensity without a precursive modulation while weak diffraction spots from the nuclei of the zeta phase appear superimposed on the sheet with a definite positional relation to the diffraction spots from the beta' phase promising aspects as well as the limits of the method applied to time-resolved measurements of structural changes are discussed.3. ALCHEMI(Atom Location by Channeling Enhanced MIcroanalysis) has been successfully applied for determination of site occupancies of Cu and Zn atoms in a shape memory alloy of Cu-21Au-45Zn (at. %) ; Zn atoms occupy the body-center sites, and Cu atoms the corner sites.

各种材料的相变机理已被各种先进的实验技术所研究。下面简要介绍在这项合作研究中取得的成果的一些例子。用中子衍射和散射实验研究了NiAl、ZrNb和FePd金属间化合物的结构和晶格动力学。在从体心立方相到马氏体相的转变温度附近发现了介观尺度的结构波动。这种波动被称为异相波动，这被认为是马氏体相变的特征。成像板和同步辐射源的组合已被证明是强大的观察漫散射的二维强度分布的变化。在从β '相到zata相的结构转变过程中连续观察到具有B2型结构的AgZn单晶的X射线漫散射。已经在以600秒的时间间隔拍摄的一系列图案中示出了平行于（111）当来自ζ相的核的弱衍射斑点以与来自β ′相的衍射斑点的确定位置关系叠加在薄片上时，讨论了应用于结构变化时间分辨测量的方法.本文应用原子定位增强显微分析法（ALCHEMI）成功地测定了Cu-21 Au-45 Zn形状记忆合金中Cu和Zn原子的占位位置。Zn原子占据体心位置，Cu原子占据角位。