EVOLUTION OF MICROSTRUCTURES AND MACROSEGREGATION IN SQUEEZE CASTING OF AL ALLOYS

摘要

Microstructural evolution and macrosegregation formation in solidification of Al alloys under high pressures were investigated. A stochastic model was developed in order to predict the formation of solidification grain structures and the columnar to equiaxed transition of Al-4.5wt%Cu and Al-7wt%Si alloys in squeeze casting. The predicted solidification grain structures under the various process conditions were compared with those obtained experimentally. The effects of process variables on the formation of macrodefects, such as shrinkage defects and macrosegregation were also investigated in squeeze casting of an Al-4.5wt% alloy. It was found that two types of macrodefects such as shrinkage cavity and macrosegregation can occur in squeeze casting under unsuitable process conditions.