Effect of strontium and melt purification on the solidification microstructure of hypereutectic Al-Si alloys

The combined effect of Sr and melt purification on the solidification structure of hypereutectic Al-Si alloys was studied by optical microscopy, scanning electron microscopy, X-ray diffractometry, and differential scanning calorimetry. The results showed that different strontium contents have a certain inhibitory effect on the precipitation of primary silicon in Al-20Si alloy. A strontium content of 0.3 wt% completely inhibited the precipitation of primary silicon in Al-16Si alloy. The synergistic effect of melt purification and 0.3 wt% Sr eliminated primary silicon from the solidified structure of Al-Si alloy with a silicon content of less than 20 wt%. It also transformed the solidified structure of Al-20Si alloy into pseudo-eutectic. Therefore, the synergistic effect of an appropriate amount of Sr and melt purification suppressed the precipitation of primary silicon in hypereutectic Al-Si alloys.