中文摘要：

采用SCN-5％Water（原子分数）透明模型合金和Sn-15％Pb（质量分数）合金对机械搅拌条件下凝固组织形态演化过程分别进行了实时动态观察和淬火金相组织分析．实验结果表明，在强烈机械搅拌作用下，两类实验合金在凝固过程中最早观察到的初生组织均为球晶组织．从实验上证实了通过适当的搅拌可直接获得球状晶组织；同时，在实验条件范围内，搅拌的进行还可促进球晶组织在相对较高温度下产生．根据凝固界面形态稳定性理论对球晶组织形成机制的分析表明：熔体中初生固相的旋转运动有利于提高液-固界面的稳定性，促进凝固组织保持球状稳定生长．

英文摘要：

Morphological evolutions during the solidification of succinonitrite-5%water （atomic fraction） transparent alloy and Sn-15%Pb （mass fraction） alloy under mechanical stirring were investigated experimentally by in situ observation and quenching, separately. The results showed that the primary solidified microstructures have a globular shape when the strong convection was induced by mechanical stirring. According to the morphological stability theory, the formation mechanism of globular microstructure was discussed. The analysis indicated that the rotation of primary microstructure in a shear flow induced a stabilizing effect on the morphological instability at the solid-liquid interface and promoted the globular growth of solidification microstructure.