抄録
The critical fraction solid, below which the primary solid and liquid flow concurrently during the solidification of Ai-Si alloy ingot, has been investigated in relation to the macrostructure of the ingot. The critical fraction solid was estimated by simulating the shape of the shrinkage depression of the conventionally cast ingots. The critical fraction solid varied from 0.05 to 0.40 when the macrostructure of the Al-3mass%Si alloy ingot changed from columnar to fine equiaxed morphology. It was also found that when the semi-liquid region disappeared, where the fraction solid was below the critical value, the remaining zone where the fraction solid is less than 0.67 had relatively high porosity.
