Effects of Si content and gas dissolution on shrinkage morphology of hypoeutectic Al-Si alloys

Hypoeutectic Al-Si alloys vacuum degassed and gas enriched were cast into conical shell molds. The castings having different quantities of gas porosities show nearly the same total shrinkage volume which decreases at higher Si contents. Pure aluminum and Al-10%Si alloy permit an unchanged volume of external shrinkage and reduced volumes of internal shrinkage with an increase in porosity volume. Al-4%Si and Al-7%Si alloys permit unchanged volumes of internal and external shrinkages respectively at lower and higher porosity levels. The volumes of internal shrinkage at higher porosity levels and of external one at lower porosity levels decrease with an increase in porosity volume. The porosity changes from a concentrated type to dispersed one with an increase in porosity volume. The gas dissolved in the melt has remarkable effects on the shrinkage morphology.