Stochastic modeling of columnar-to-equiaxed transition in Ti–(45–48 at%) Al alloy ingots

A two-dimensional (2-D) stochastic model of macro–micro type for predicting the columnar-to-equiaxed transition (CET) during solidification processes of the large size Ti–(45–48 at%) Al alloy ingots is developed in this paper. The macroscopic part is based on a finite differential method (FDM) for modeling of heat transfer. The microscopic part consists of a cellular automaton method (CA) for modeling of nucleation and growth. The formation of a shrinkage cavity at the top of ingot is taken into account. The effects of casting variables on 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, mold-preheated temperature and convection, and increasing the thermal conductivity of mold, superheat and heat transfer coefficient.