Effect of local chilling on morphology of primary α(Al) in semi-solid A356 alloy

The semi-solid slurry of A356 alloy was prepared by low superheat pouring and slightly electromagnetic stirring, in which a pure copper rod was used to produce local chilling. The effect of chilling by the rod on morphology and size of primary alpha(Al) in A356 was researched. The results indicate that the chilling by the rod remarkably affects the morphology and the size of primary alpha(Al). Primary alpha(Al) with particle-like shape is distributed uniformly in A356, and there is no transient area in structure morphology. Compared with the samples prepared without the local chilling, the nucleation rate, morphology and grain size of primary alpha(Al) in A356 prepared by low superheat pouring and slightly electromagnetic stirring with the rod are markedly improved. Under the condition of chilling, the pouring temperature can be suitably raised to obtain primary a(Al) with particle-like shape.