机械合金化Fe100-xCux体系的X射线吸收精细结构研究

利用X射线吸收精细结构(XAFS)方法研究机械合金化制备的Fe_100-xCu_x(x=0,10,20,40,60,70,80,100,x为原子百分比)合金中Fe和Cu原子的局域环境结构.对于Fe_100-xCu_x(x≥40)二元混合物,球磨160h后,Fe原子的近邻配位结构从bcc转变为fcc,但Cu原子的近邻结构保持其fcc不变.与之相反,在Fe₈₀Cu₂₀和Fe₉₀Cu₁₀(x≤20)合金中,Fe原子的近邻配位保持其bcc结构而Cu原子的近邻配位结构从fcc转变为bcc结构.XAFS结果还表明,fcc结构的Fe_100-xCu_x样品中Fe的无序因子σ(0.0099nm)比bcc结构的Fe_100-xCu_x中的σ(0.0081nm)大得多;并且在机械合金化Fe_100-xCu_x(x≥40)样品中Fe原子的σ(0.0099nm)比其Cu原子的σ(0.0089nm)大.这表明机械合金化Fe_100-xCu_x样品中Fe和Cu原子可以有相同的局域结构环境但不是均匀的过饱和固溶体,而是由Fe富集区和Cu富集区组成的合金.我们提出互扩散和诱导相变机理来解释在球磨过程中Fe_100-xCu_x合金产生从bcc到fcc和从fcc到bcc变化的结构相变关键词：XAFS100-xCu_x合金')" href="#">Fe_100-xCu_x合金机械合金化

LOCAL STRUCTURES OF MECHANICALLY ALLOYED Fe100-xCux SOLID SOLUTIONS STUDIED BY X-RAY ABSORPTION FINE STRUCTURE

The local structures of the immiscible Fe_100-xCu_x alloys (x=0,10,20,40,60,80 and 100)produced by mechanical alloying have been investigated by XAFS.For the Fe_100-xCu_x(x≥40) alloys,the local structures around Fe atoms change from bcc structure to fcc one,and the Cu atoms maintain the original coordination geometry after milling for 160 h. On the contrary, the local structures around Cu atoms in both Fe₈₀ Cu₂₀and Fe₉₀ Cu₁₀ alloys appears a transition from fcc to bcc structure.We found that the disorder factor σ(0.0099nm)of fcc Fe—Cu phase is larger than that (0.0081nm) of bcc Fe—Cu phase,and the σ(0.0099nm) around Fe atoms is larger than that (0.0089nm) of Cu in the Fe_100-xCu_x(x≥40) alloys. This suggests that the mechanically alloyed Fe_100-xCu_x alloys is not a homogeneous supersaturated solid solution,but consists of Fe-rich and Cu-rich regions for various compositions.A possible mechanism for bcc-to-fcc and fcc-to-bcc changes in Fe_100-xCu_x alloys is discussed in relation to the interdiffusion and transition induced by the ball milling.