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采用光学显微镜(OM),扫描电子显微镜(SEM)和电子探针(EPMA)等手段分析研究773 K下Mg-Gd二元系的反应扩散现象。结果表明:Mg-Gd扩散偶在773 K下热处理12~48 h后均形成四层明显的第二相扩散层,分别为Mg5Gd、Mg3Gd、Mg2Gd和Mg Gd相。各扩散层厚度δi(i分别代表Mg5Gd,Mg3Gd,Mg2Gd和Mg Gd相)与热处理时间t1/2呈正比,表明扩散层的生长由扩散速率所控制。同时各扩散层厚度占总扩散层厚度的比例基本保持不变,不随时间的延长而变化,这表明当热处理温度一定时,各扩散层的生长方式保持不变。最后利用Matano法计算Gd在不同相中的扩散系数。
The reaction diffusion phenomenon of Mg-Gd binary system at 773 K was studied by optical microscope (OM), scanning electron microscopy (SEM) and electron probe (EPMA). The results show that four layers of Mg2Gd, Mg3Gd, Mg2Gd and MgGd phases are formed after the Mg-Gd diffusion couple is annealed at 773 K for 12-48 h. The thickness of each diffusion layer δi (i represent Mg5Gd, Mg3Gd, Mg2Gd and Mg Gd, respectively) is proportional to the heat treatment time t1 / 2, indicating that the diffusion layer growth is controlled by the diffusion rate. At the same time, the ratio of the thickness of each diffusion layer to the thickness of the total diffusion layer remains basically unchanged and does not change with time, indicating that the growth mode of each diffusion layer remains unchanged when the heat treatment temperature is constant. Finally, Matano method was used to calculate the diffusion coefficient of Gd in different phases.