Modeling of microstructure evolution in eutectic and peritectic solidification

A modified cellular automaton (MCA) model is proposed and applied to simulate the microstructure evolution during eutectic and peritectic solidification of alloys. The present MCA model accounts for the aspects including the nucleation of a new phase and the growth of primary dendrites and the subsequent eutectic or peritectic transformation, as well as the coupling between phase transformation and solute redistribution. Different growth algorithms are employed for the growth of non-faceted and faceted crystals. The present model is applied to simulate the microstructure formation of a regular non-faceted/non-faceted model eutectic alloy, an irregular non-faceted/faceted hypoeutectic Al-7mass%Si alloy and a peritectic Fe-0.3mass%C alloy. The simulation results reveal a wide range of realistic eutectic and peritectic growth phenomena, such as the selection of eutectic lamellar spacing in a regular eutectic alloy, the irregular eutectic morphology and the eutectic nucleation mode in the modified and unmodified hypoeutectic Al-7mass%Si alloy. It is also found that beta phase nucleates around the primary alpha phase and laterally grows from both the liquid and alpha solid phase during peritectic solidification.