The influences of mechanical stirring on microstructure of primary silicon in hypereutectic Al-Si alloys were analyzed.The microstructure of modified and un-modified Al-30 Si alloys were observed by optical microscope and metallographic analysis software.The results show that the primary silicon particles can be refined and spheroidized obviously by controlling the stirring temperature and speed

where the refinement of grain is dependent on the higher speed and lower temperature

and spherodization of primary phase is controlled by the higher speed and higher temperature.With stirring at 900r/min and680 ℃

primary silicon particles exhibit the satisfied refinement in un-modified Al-Si alloy

while with at900r/min and 765 ℃

primary silicon particles have the acceptable spheroidization effects in modified Al-Si alloy.