Effect of low-voltage alternating current pulse treatment on the macrostructure of A357 alloy

Based on the A357 aluminum alloy, the effect of low-voltage alternating current pulse (LVACP) on the macrostructure of alloy was investigated by using LVACP treatment. The experimental results indicate that the macrostructure for whole ingot could be refined with LVACP and there was a threshold value and a saturation value for the current density used to refine grain. Although the pulse current was applied to different stages of the solidification, the refinement effect occurs only during the nucleation stage. The effect of current density on grain density was similar to that of undercooling. The nucleation barrier was reduced by providing an additional energy during the nucleation stage, which would lead to a multiplication of the crystal nuclei and refinement of grain.