铜铬合金时效早期阶段析出相的形貌和结构研究

Morphological Structure of Precipitation at Early Stage of Aging in Cu-Cr Alloy Materials

用快速凝固法制备不同铬含量的三种铜铬合金粉体Cu-0．34Cr，Cu-0．76Cr，Cu-1．56Cr，并对合金进行时效，用高分辨电镜观察不同时效阶段的结构。在时效的前期阶段观察到两种长周期调制结构。调制结构Ⅰ是在基体的晶体排列上加入了一个微小的调制形成的，是一个沿三个[111]晶向，周期为7～9的三维无公度调制结构。调制结构Ⅱ是典型的DO3型超结构，和基体具有N—W晶体学位向关系，能谱分析表明调制结构Ⅱ不是共格的BCC铬相，其成分组成[Cu]：[Cr]接近4：1。时效析出贯序可以表达为：FCC铜基固溶体（无序结构）→FCC演化的调制结构Ⅰ→调制结构Ⅱ（典型的DO3结构）→BCC的Cr单质析出相。证明了过饱和铜铬合金时效过程的析出机制是以两个亚稳结构为过渡相逐步转变的，而不是“共格的Cr FCC相”或“共格的Cr BCC相”。

The copper-chrome alloy powders of Cu0.34Cr, Cu0.76Cr, Cu1.56Cr are prepared by rapid solidification. Aging-characteristics are obtained, the structure is varied with aging time on TEM. Two modulated structures are found in presaging time, which are ordered intermetallic phase. The modulated period of modulated structure Ⅰ is about in the 7- 9, and the orientation is three sorts of crystal orientation [111]. The modulated structure Ⅱ is a DO3 super structure. The crystallographic relationship between the modulated structure Ⅱ and matrix stands to the well known N-W relation and its stoichiometry is near 4 ： 1. The precipitation sequence is identified by： FCC Cu solid solution→modulated structure Ⅰ evolved from FCC→modulated structure Ⅱ （DO3 super structure）→BCC precipitate of simple substance Chromium. It is indicated that the precipitation mechanism and principle are transit by two modulated structures, but not by FCC lattice Chromium incoherent with matrix and BCC lattice Chromium incoherent with matrix but.