Effect of Solidification Pressure on Microstructure and Iron-Bearing Phase of A357 Alloy

The investigation was carried out to study the effects of solidification pressure and cooling rate on microstructure of A357 alloy during counter-gravity casting solidification process. The results show that, from the center to the edge of samples, the secondary dendrite spacing λ2 reduced and microstructure was refined with the cooling rate increasing; as the solidification pressure increased from 1.55 kPa to 30.90 kPa, λ2 decreased and the morphology of iron-bearing phase changed from needle-like to skeleton shape; the microstructure was refined more remarkable with the increase of solidification pressure and cooling rate.