Atomistic Mechanisms of Phase Transformations in Metals and Alloys

各种材料的相变机理已经用各种先进的实验技术进行了研究。下面简要介绍了在这项合作研究中获得的一些结果。利用中子衍射和散射实验对NiAl、ZrNb和FePd金属间化合物进行了结构和晶格动力学研究。在bcc-相向马氏体相转变的温度附近，发现了介观尺度上的结构波动。这种波动被称为异相波动，它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在二维漫射散射强度分布的变化的观测。研究了具有b2型结构的AgZn单晶在β′相到zata相结构转变过程中的x射线散射。它已被证明在一系列的模式在一个时间间隔的600年代漫射强度表扩展平行于(111)relplane逐渐失去了它的强度没有先驱调制而弱衍射斑点的核ζ相叠加显示在表的一个明确的位置与β”相的衍射斑点承诺方面的限制以及方法应用于时间分辨测量结构变化discussed.3。短句来源利用通道增强微分析技术（Atom Location by Channeling Enhanced MIcroanalysis）成功地测定了Cu- 21au - 45zn （at）形状记忆合金中Cu和Zn原子的位占率。%);锌原子占据体中心位置，Cu原子占据角位。

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.