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采用金相显微镜、扫描电镜、X射线衍射仪和同步热分析仪研究了Sb变质对Mg_2Si/AZ91D复合材料中Mg_2Si相的影响,探索了变质机理。结果表明:0.2%Sb变质使Mg_2Si/AZ91D复合材料中初生Mg_2Si由粗大的枝晶状变成细小的多边形状,共晶Mg_2Si的形貌由粗大的汉字状变成针状、团絮状、短杆状、蠕虫状和颗粒状。继续增加Sb含量,对初生Mg_2Si的形状和尺寸影响不大。但是增加Sb含量使得颗粒状的共晶Mg_2Si数量增多,尺寸减小,分布更均匀。加入Sb变质剂后,Mg_3Sb_2可作为初生Mg_2Si的形核核心,细化晶粒。共晶Mg_2Si的凝固开始温度降低,其形核过冷度增大,形核率增加。
The effect of Sb modification on the Mg_2Si phase in Mg_2Si / AZ91D composites was investigated by metallographic microscope, scanning electron microscopy, X-ray diffraction and synchronous thermal analyzer. The mechanism of metamorphism was explored. The results show that the morphology of primary Mg_2Si in Mg_2Si / AZ91D composites changes from coarse dendrites to fine polygons, and the morphology of eutectic Mg_2Si changes from coarse Chinese characters to acicular, flocculent and short Rod-shaped, worm-shaped and granular. Continue to increase the Sb content, the shape and size of primary Mg_2Si little effect. However, the increase of Sb content makes the number of eutectic Mg 2 Si particles increase, decrease in size and distribute more evenly. After adding Sb modifier, Mg_3Sb_2 can be used as the nucleus of primary Mg_2Si nucleation and grain refinement. The eutectic Mg_2Si solidification start temperature decreases, the nucleation supercooling increases, the nucleation rate increases.