Sm_2Fe_(17)和Sm_(10.5)Fe_(88.5)Zr_(1.0)的氮化行为

The nitrogenation behaviour of Sm_2Fe_(17) and Sm_(10.5)Fe_(88.5)Zr_(1.0)

通过真空电弧炉制备了Sm2Fe17和Sm10.5Fe88.5Zr1.0母合金,铸态Sm2Fe17先经均匀化处理后再氮化,而Sm10.5Fe88.5Zr1.0则不经均匀化退火而直接在高纯氮气中氮化。运用扫描电子显微镜和X射线衍射技术对其氮化行为进行了研究。薄片扩散实验表明氮在Sm2Fe17中的扩散要比在Sm10.5Fe88.5Zr1.0中的扩散快。运用Fick第二定律通过理论计算得出直径为20μm的Sm2Fe17合金和Sm10.5Fe88.5Zr1.0合金球形粉末粒子,实现充分氮化的时间为10h和16h。实际粉末实现完全氮化的时间要比理论计算的时间少。这和粒径分布、颗粒表面状态、氮化过程产生的微裂纹以及实际条件和理想条件的差异有关。对于直径为20μm的粉末,氮化时间为6h时氮化已基本完成,氮化时间过长,Sm2Fe17Nx会发生分解。

Sm_2Fe_(17) and Sm_(10.5)Fe_(88.5)Zr_(1.0) prealloys were prepared by melting in a vacuum arc furnace. The nitrogenation was carried out in ultra pure nitrogen, while the cast Sm_2Fe_(17) was additionally homogenized. The nitrogenation behaviour was investigated by using scanning electron microscopy and X-ray diffraction technique. Diffusion experiments on thin plates showed that the diffusion of nitrogen in Sm_2Fe_(17) was faster than it in Sm_(10.5)Fe_(88.5)Zr_(1.0).The sufficient nitrogenation time for Sm_2Fe_(17) and Sm_(10.5)Fe_(88.5)Zr_(1.0) spherical particles of 20μm diameter would be 10h and 16h respectively, according to the theoretical calculations by using Fick second law. The nitrogenation time to obtain fully nitrided alloy for factual powders was less than predicted by calculations. The difference between the idealized powders used for theretical calculations and real powders was attributed to the particle size distribution, surface state, microcracks caused by nitrogenation and the factual condition of the milled powder. For the spherical particles of 20μm diameter, the nitrogenation was accomplished basically when the time was 6h. Sm_2Fe_(17)N_x would decompose if the nitrogenation time was too long.