Fe100—xCux纳米合金材料的结构研究

利用XAFS方法研究机械合金化方法制备的Fe10 0 -xCux(x =0、1 0、2 0、40、6 0、70、80、1 0 0 ,x为原子百分比 )合金中Fe、Cu原子的局域环境结构随组成的变化 .对于Fe10 0 -xCux 二元混合物 ,当x 40时 ,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 ,当x 2 0时 ,Fe原子的近邻配位保持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Fe10 0 -xCux 中Fe的无序因子σ ( 0 0 0 99nm)比bcc结构的Fe10 0 -xCux 中的σ ( 0 0 0 81nm)大得多 ;并且在同一机械合金化Fe10 0 -xCux(x 40 )样品中Fe原子的σ ( 0 0 0 99nm)比Cu原子的σ ( 0 0 0 89nm)大 .这表明机械合金化的Fe10 0 -xCux 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fcc或bcc合金相同时存在Fe富集区和Cu富集区 .

Structural Studies of Nanometeric Fe_(100-x)Cu_x Alloys

The local structures of the immiscile Fe100-xCux alloys (x= 0,10, 20, 40, 60, 80 and 100) produced by mechanical alloying have been investigated by XAFS. For the Fe100-xCux (x40) alloys, the local structures around Fe atoms change from a bcc structure to an fcc one and the Cu atoms maintain the original coordination geometry after milling for 160 hours. On the contrary, the local structures around Cu atoms in both Fe80Cu20 and Fe90Cu10 alloys show a transition from fcc to bcc structure. It is found that the disorder factor σ(0.099 !) of fcc Fe-Cu phase is larger than that (0.081 !) of bcc Fe-Cu phase, and the σ(0.099 !) around Fe atoms is larger than that (0.089 !) of Cu atoms in the Fe100-xCux (x40) alloy. This suggests that the mechanically alloyed Fe100-xCux alloy is not a homogeneous supersaturated solid solution, and consists of Fe-rich and Cu-rich regions for various compositions.