稳恒磁场对Fe-Fe50 wt.%Si扩散偶中间相生长的影响

本文考察了Fe-Fe50 wt.%Si扩散偶在1200℃ 无磁场以及稳恒磁场下扩散层生长规律. 利用真空浇注强制冷却技术制备Fe-Fe50 wt.%Si扩散偶, 将制备的扩散偶进行1200℃不同磁感应强度下的热处理. 对获得热处理后试样进行SEM与EDS线扫描分析, 结果表明, 无论无磁场还是稳恒磁场下Fe-Fe50 wt.%Si扩散偶均生成两个扩散层, 即FeSi相层和Fe-Si固溶体层, 并且发现0.8 T下的两个扩散层宽度均小于0 T磁场下试样. 按照抛物线规律, 计算了扩散偶中间扩散层的互扩散系数, 发现0.8 T磁场下FeSi相层和Fe-Si固溶体层的互扩散系数较无磁场下 分别降低了26.7%与34.1%. 通过对磁吉布斯自由能的计算, 发现0.8 T磁场对扩散激活能Q的影响不足以影响扩散过程. 但扩散过程中原子振动频率ν会受到磁场的影响, 进而影响扩散常数D₀, 磁场对原子振动频率的影响可以用拉莫尔旋进理论进行解释. 关键词： Fe-Fe50wt.%Si扩散偶 稳恒磁场 FeSi相 Fe-Si固溶体

Effect of magnetic field on growth of intermetallic compound layers in Fe-Fe50wt.%Si diffusion couple

In this paper, Fe-Fe50 wt.%Si diffusion couples are subjected to 1200℃ heat treatment in static magnetic field. Fe-Fe50 wt.% Si diffusion couples were prepared by vacuum casting technology and later sectioned and polished for scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies before heat treated. Microstructures of the treated samples which were polished first were analyzed by SEM and EDS; results show that the phase components of the interfacial intermetallic compound layers are FeSi phase layer and Fe-Si solid solution layer whether the samples were treated with or without magnetic field, and the layer widths in the samples treated with magnetic field are smaller than those without magnetic field. According to the parabolic law, the interdiffusion coefficients of the interfacial intermetallic compound layers were calculated and the interdiffusion coefficients of FeSi phase and Fe-Si solution under a field of 0.8 T are reduced by 26.7% and 34.1%. The Gibbs energy due to applied field was calculated, data analysis shows that the reduction of interfacial intermetallic compound layer coefficients is attributed to the decrease of frequency factor, not the activation energy. Decrease in layer thickness decrease is suggested to be related to the retardation of atomic diffusion resulting from the magnetic field, and a possible theory based on Larmor precession is given to explain this effect.
Keywords： Fe-Fe50 wt.%Si couple static magnetic field FeSi phase Fe-Si solution layer