Modeling of globular and dendritic structure evolution in solidification of an Al-7mass%Si alloy

The evolution of globular and dendritic structures in solidification of an Al-7mass%Si alloy has been investigated by a modified cellular automaton model (MCA). Besides retaining the probabilistic aspects of the classical CA model for the heterogeneous nucleation and the preferential growth orientations of the nuclei, the present MCA model is coupled with the curvature, the solute partition between liquid and solid as well as diffusion in both phases. The effects of constitutional undercooling and curvature undercooling are incorporated on the equilibrium interface temperature. The relationship between the growth velocity of a dendrite tip and the local undercooling is calculated according to the KGT (Kurz-Giovanola-Trivedi) model. The finite volume method, coupled with the cellular automaton model, was used to calculate the solute field in the computational domain. The effects of pouring temperature, cooling rate, and inoculation on the growth morphology of the primary phase were studied. The simulation results were compared with those obtained experimentally. It can be concluded that the present simulation model can successfully predict the evolution of dendritic and globular structures in solidification of alloys.