Modeling of As-cast microstructure of Al alloy with a modified cellular automaton method

Abstract

Microstructure modeling of aluminum alloy casting has been carried out by using a modified cellular automaton (CA) method coupled with macro heat transfer calculation. Continuous nucleation model is applied to describe heterogeneous nucleation in liquid metal. Dendrite tip growth kinetics and preferential 〈100〉 crystallographic orientation are taken into account. Therefore, the stochastic nature of nucleation process as well as the deterministic of dendrite growth is considered to simulate the crystal growth. The actual dendritic shape is substituted for the square envelope in the ordinary cellular automaton model. In addition, the coordinate transformation method is employed to describe the grain growth and to maintain it onto the original orientation of nucleus. Simulation results show that grain size is different at various positions of a step-shaped sample casting. The grain size is smaller when cooling rate is faster and vice versa, which is in good agreement with the experimental results and the solidification mechanism as well.