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采用等温-双向电磁搅拌方法处理了A356合金熔体,研究双向电磁搅拌不同作用时间对浆料组织及结晶方式的影响。结果表明:在搅拌温度595℃、搅拌功率1200 W、搅拌时间5~15 min下等温-双向电磁搅拌能制备出具有近球状初生相的A356合金半固态浆料,初生相经历长大、分离、再长大的过程,短时或长时搅拌得到的初生相粗大、分布不均匀,在合适的时间内才能制备出理想的半固态浆料。长时间的等温-双向电磁搅拌影响共晶组织的形成平衡条件,发生离异共晶,在凝固组织中出现球状或近球状初生硅。等温-双向电磁搅拌处理合金熔体产生的近球状组织是枝晶臂断裂机制和晶粒抑制生长机制共同作用的结果。
The melt of A356 alloy was treated by isothermal-two-way electromagnetic stirring method to study the effect of two-way electromagnetic stirring on the microstructure and crystallization of slurry. The results show that A356 alloy semi-solid slurry with nearly spherical primary phase can be prepared by isothermal and two-way electromagnetic stirring under stirring temperature of 595 ℃, stirring power of 1200 W and stirring time of 5-15 min. The primary phase undergoes growth and separation, Re-growth process, short-term or long-time mixing of the primary phase coarse, uneven distribution, in the right time to prepare the ideal semi-solid slurry. Long time isothermal - two-way electromagnetic stirring affect the formation of eutectic equilibrium conditions, the occurrence of divorced eutectic, in the solidified microstructure of spherical or nearly spherical primary silicon. Near-spherical microstructure produced by the isothermal-two-way electromagnetic stirring alloy melt is the result of the combined action of the dendritic arm fracture mechanism and the grain growth inhibiting mechanism.