机械合金化Cu-Sn二元形状记忆非晶态合金的XAFS研究

利用X射线吸收精细结构(XAFS)方法研究了机械合金化(Mechanical alloying，MA)方法制备的Cu-Sn二元金属合金在球磨过程中的结构变化。研究结果定量地表明，随着球磨时间的增加，Cu-Cu的键长逐渐变大，Cu第一近邻Cu-Cu配位数减小；Cu-Sn配位数逐渐增大，Cu与Sn的合金化程度和均匀性也随之增加。球磨4h后，Cu-Cu的配位数由Cu粉的12降低为7．4，键长由2．55A增加到2．63A；球磨12h后，Cu-Cu的配位数降低到6．4，Cu-Sn的配位数由O变到5．1，键长约为2．8A左右；球磨72h的结果与球磨12h的结果相近，说明Cu与Sn的互扩散过程基本达到平衡，形成组成近似于Cu6Sn5的非晶合金。

XAFS study on local structures of mechanically alloyed Cu-Sn amorphous shape memory alloys

The local structures of mechanically alloyed Cu-Sn mixtures have been investigated by X-ray absorption fine structure (XAFS) technique. The result indicates that the bond length of the Cu-Cu first shell slightly increases and the coordination number of the Cu-Sn first shell largely increases with the milling times for the Cu-Sn alloys. This means that the inter-diffusion between Cu and Sn grains, driven by mechanical alloying, results in forming Cu-Sn alloy. After milling 4h, the coordination number and the bond length of the Cu-Cu first shell change from 12 to 7.4 and from 2.55 ?to 2.60 ?for the Cu-Sn alloys, respectively. After 12h milling, the coordination number of the Cu-Cu first shell decreases to 6.4 while that of the Cu-Sn first shell increases to 5.1 and its bond length is about 2.80 for the Cu-Sn alloy. Furthermore, the XAFS result for the Cu-Sn alloy milled for 72 h is similar to that for 12 h. This implies that the inter-diffusion between Cu and Sn grains has nearly reached the equilibrium and an amorphous Cu-Sn alloy of Cu6Sn5-like is formed.