The effects of mixed rare earth(RE), strontium and their composite modifier on eutectic silicon morphology of Al-24％Si alloy were studied with optical microscopy and SEM. The results show that the eutectic silicon in the alloy without modification treatment was coarse block-shape, loose arrangement and uneven. After it was modified by mixed RE, the shape of the eutectic silicon near primary silicon was fine particulate, whereas that far away from primary silicon was rod. The shape of the eutectic silicon after modified by Sr was short rod with secondary or tertiary branches. The morphology of eutectic silicon treated by composite modifier was smooth roundpole shape, its size was larger than that of treated by RE, and its amount was less than that of treated by Sr.%采用光学显微镜和扫描电子显微镜研究了混合稀土、锶及两者的复合变质对Al-24%Si合金中共晶硅形貌的影响.结果表明:未变质时合金中共晶硅呈粗大的板块状,排列疏松,不均匀;经混合稀土变质后,分布在初生硅周围的共晶硅呈细小颗粒状,而远离初生硅的区域,共晶硅主要呈杆状;经锶变质后,共晶硅主要呈短杆状且存在二次甚至三次分枝;经复合变质后,共晶硅呈光滑圆杆状,但尺寸较稀土变质时增大,且数量较锶变质时有所减少.
展开▼
