机械合金化Fe70Cu30体系的结构研究

利用XAFS方法对机械合金化Fe70Cu30样品中Fe,Cu原子的局域环境结构随球磨时间的变化情况进行了研究，结果表明，由于Fe和Cu原子分别向fcc的Cu相和bcc的Fe相的扩展，Fe和Cu同时存在于fcc和bcc结构相中，介Fe和Cu原子的局环境结构随球磨时间的级很大判别，球磨2h后，样品中73％的Cu原子在fcc相，27％的Cu原子在bcc相，21％的Fe原子在fcc相，79％的Fe原子在bcc相，球磨5h，fcc相的Cu原子减少到59％，fcc相的Fe原子则略有增加，为29％，球磨10h后，fcc相的Cu原子比例又增加到86％，fcc相的Fe原子也迅速增加到51％，说明大量的Cu原子扩散到bcc的Fe相后诱导其产生fcc结构相变，继续球磨到20h，样品中Cu原子和Fe原子在fcc和bcc相的比例基本保持不变，这些结果说明，在球磨过程中Fe和Cu并未形成均一的固溶体，同时存在着fcc的Cu富集区，fcc的Fe富集区和bcc的Fe富集区。

Local Structures of Mechanical Alloying Fe_(70)Cu_(30) System Studied by XAFS

The local structures of the Fe70Cu30 alloy produced by mechanicalalloying have been investigated by XAFS. The results show that Fe atoms and Cu atoms coexist in both bcc and fcc phases, but the local structures of Fe atoms and Cu atoms depend on the milling time t. The following data are obtained from the curve fitting. 73% of the Cu atoms in the sample is fcc phase and 27% of the Cu atoms is bcc phase while 21% Fe atoms is fcc phase and 79% Fe atoms is bcc phase in Fe70Cu30 when t=2h. After 5 hours of milling, the fcc Cu atoms drop to 59% while the fcc Fe rise to 29%. When milling time is up to 10h, the fcc Cu atoms increase to 86% and the fcc Fe atoms also increase rapidly to 51%, which suggests that a large number of Cu atoms diffusing to bcc α-Fe induce the local structures of Fe atoms to transfer from bcc to fcc. When t=20h, the percentage is almost constant compared with the sample milled 10h. These results indicate that the mechanically alloying Fe70Cu30 alloy is not a homogeneous supersaturated solid solution, but consists of fcc Cu-rich ,fcc Fe-rich and bcc Fe-rich regions.