Investigation of Solid-State Alloying in Transition Metal Binary Alloy Composite Films by High Resolution and Analytical Electron Microscopy.

为了更有效地加速实验，设计并建造了一台配备大容量电子束蒸发器的高真空沉积装置。自1990年以来，它已成功地用于制备由5000埃厚的Bi层和2000埃厚的Mn层组成的复合双层厚膜，通过Bi和Mn的共沉积，发现当Bi和Mn的成分在65 - 85at%Mn之间时，可获得非晶态合金膜。当升温至180 ℃时，发生“成核和晶粒生长”型晶化，得到的晶体具有新的亚稳六方点阵，a = 19.97 A，c = 4.49 A。这个大晶格中的原子排列是由它的电子衍射图、高分辨率电子显微照片及其计算机模拟确定的。在连续沉积法制备的Mn-Bi双层复合薄膜中，虽然平衡相图中只描述了一种铁磁MnBi相，但由于在Bi熔点以下的低温加热，固态合金化得到了多达四种新的合金相。它们包括a = 17.26 A，c = 10.21 A的长周期四方相，以及具有12重对称性的准晶，这将与长周期四方相有密切的结构关系。亚稳六方相的结构分析是仅用电子显微镜进行分析的少数例子之一。具有十二重对称性的准晶是世界上首次观察到的准晶，目前正在《哲学杂志快报》上发表。参照σ相结构等，寻找长周期四方相的原子排列，并开始了Fe-Zn系的沉积实验，以期对镀锌钢板的工业化生产有所贡献。

In order to accelerate experiments more effectively, a high-vacuum-deposition apparatus equipped with an electron-beam-evaporator with a large capability was designed and constructed. It has been successfully used, since 1990, for preparing composite double layer thick films consisting of a Bi layer 5000 A and of a Mn layer 2000 A in thickness.By co-deposition of Bi and Mn, it was found that non-crystalline alloy films are obtained when their composition is between 65 and 85 at% Mn. When warmed up at 180^ﾟC, crystallization of the "nucleation and grain growth" type takes place and obtained crystals have a new metastable hexagonal lattice of a = 19.97 A, c = 4.49 A. Atomic arrangement within this large lattice was determined from its electron diffraction patterns, high resolution electron micrographs and their computer simulation. In composite double layer Mn-Bi films prepared by successive deposition, as many as more than four kinds of new alloy phases were obtained by solid-state alloying due to low temperature heating below the melting point of Bi, although only one phase, ferromagnetic MnBi, is described to exist in the equilibrium phase diagram. They include a long-period tetragonal phase with a = 17.26 A, c = 10.21 A, and a quasicrystal having twelve-fold symmetry, which will have intimate structural relation to the long-period tetragonal phase.Structure analysis of the metastable hexagonal phase is one of a few examples of performing the analysis only by electron microscopy. The quasicrystal with twelve-fold symmetry is the one first observed in the world and is now in press in Philosophical Magazine Letters. Atomic arrangement of the long-period tetragonal phase is being looked for referring to the sigma-phase structure and so on. Deposition experiment of Fe-Zn system was just started in an aim of making some contribution to industrial manufacturing of galvanized steel sheets.