Simulation of columnar-to-equiaxed transition in solidified Al–Cu alloy ingots by stochastic model

Abstract

A two-dimensional stochastic model for the prediction of the columnar-to-equiaxed transition (CET) during solidification processes of Al–Cu alloy ingots is developed, based on a finite differential method (FDM) for macroscopic modelling of heat transfer and a cellular automaton method (CA) for microscopic modelling of nucleation and growth. The formation of a shrinkage cavity at the top of the ingot is taken into account. The effects of the casting variables on the CET are presented and discussed. A quantitative relation between CET position and casting variables is obtained. The columnar zone is found to expand with decreasing alloy composition and mould preheated temperature, and with increasing superheat and initial heat transfer coefficient. However, increasing the mould preheated temperature in a particular range has a negligible influence on the CET. With a low rate of heat extraction, the CET is found to be independent of melt superheat.