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用扫描电镜 (SEM )背散射成像技术对金属型铸造树枝晶SiCp/ZA2 7复合材料部分重熔过程中的组织变化进行了观察。结果表明 :在 460℃加热过程中 ,因晶界共晶组织向初生晶的扩散 ,造成树枝晶二次枝晶臂和晶粒间的快速合并 ,形成无明显晶界的组织 ,将分布于枝晶间的SiCp 裹入晶内 ,接着 ,剩余共晶组织开始熔化 ,组织发生分离 ,形成不规则的大块状组织 ,并将SiCp 返还于晶粒间的液相中 ,随后 ,因不规则组织突出部位 (曲率大 )的溶化 ,组织趋于圆整 ,最后经球状化形成尺寸较大的近球状颗粒。还从相变角度分析了组织的演变过程。
Scanning electron microscopy (SEM) backscatter imaging was used to observe the microstructural changes in the partial remelting process of the metal cast dendritic SiCp / ZA2 7 composites. The results show that during the heating process at 460 ℃, the secondary dendrite arm and the grains are rapidly merged by the diffusion of the grain boundary eutectic structure to the primary crystal, forming a structure with no obvious grain boundary and distributing in the branch The intergranular SiCp is entrapped in the crystal, and then the remaining eutectic structure starts to melt and the structure is separated to form an irregular bulk-like structure, and the SiCp is returned to the liquid phase between the crystal grains. Subsequently, due to the irregular structure Prominent parts (large curvature) of the melt, the organization tends to round, and finally spheroidized to form a larger size of nearly spherical particles. It also analyzes the evolution of the organization from the perspective of phase transformation.