Influences of processing parameters and modification on microstructure of primary silicon in hypereutectic Al-Si alloys were investigated by optical microscope and Image Pro metallographic analysis software.The results show that the primary Si can be refined significantly by controlling pouring temperature

mold temperature and addition content of modifier

and effect of modifier is much greater than pouring temperature

mold temperature.When the pouring temperature is 760℃or mold temperature is200 ℃

the primary silicon particle size in solidification structure is less than 90μm

while phosphate salts modifier is 0.8% or Cu-14 Pmaster alloyis 0.4%

the size of primary silicon is less than 20μm.