The refining effects and action mechanism of high-intensity ultrasonic on the primary Si in hypereutectic Al-Si alloy were investigated by treating Al-20Si melt with different sonophoresis ways. The results show that the nucleation rate in the alloy during solidification process can be increased by high-intensity ultrasonic treatment

where the shape of the primary Si is changed from the coarse plank structure into spherical ones with uniform distribution and the decrease of grain size. Refining effects are significantly different by treating with different sonophoresis methods due to the attenuation of the ultrasonic. The experimental results indicate that the primary Si is well refined with the more uniform distribution in the alloy

and the refinement area of solidification can be enlarged by treating with high-intensity ultrasonic when the ultrasonic rod is introduced with the circle movement at 1/2 of ingot casting radius to the center of melt.