用机械合金化法制备Sm—Fe合金及其晶化与氮化过程探讨

PREPARATION OF Sm-Fe ALLOY USING MECHANICAL ALLOYING AND ITS CRYSTALLIZATION AND NITROGINATION

研究了用机械合金化方法制备的Sm_2Fe_(17)合金的晶化与氮化过程。结果表明:机械合金化的Sm-Fe合金是Sm-Fe非晶相与晶态α-Fe的混合物,其成分是不均匀的,Fe在非晶颗粒外层含量较少,晶化过程包含Fe原子的长程扩散和固相反应,在适当的晶化条件下,晶化后全部转化为Sm_2Fe_(17)相。晶化过程中,可能出现六方结构的Th_2Ni_(17)型Sm_2Fe_(17)亚稳相。氮化过程由孕育期、Sm_2Fe_(17)相与其氮化物相共存、最终全部转化为氮化物相三阶段组成;在氮化过程中有十分细小的少量α-Fe析出。

The crystallization and nitrogination of a mechanically alloyed Sm-Fe alloy have been investigated. The results show that the alloy consists of amorphous Sm-Fe phase and crystalline α-Fe. The composition of the alloy is inhomogeneous, the surface of the as-milled powder is relatively poor in Fe. The crystallization process involves the long-range diffusion of iron atoms and solid state reaction. After proper crystallization, the as-milled powder transforms into a Sm_2Fe_(17) phase completely. A metastable phase, which may be a Sm_2Fe_(17) phase with the structure of hexagonal Th_2Ni_(17) type, appears during the crystallization process. Nitrogination of Sm_2Fe_(17) consists of the following processes: incubation period, coexistence of Sm_2Fe_(17) and its nitride, and transformation of residual Sm_2Fe_(17) into nitride phase. During nitrogination small amount of very fine α-Fe segregates.