Modeling of microstructural evolution during divorced eutectic solidification of spheroidal graphite irons

A two-dimensional multiphase cellular automaton model is proposed for the simulation of microstructural evolution during divorced eutectic solidification of spheroidal graphite (SG) irons. The model adopts a previously proposed local solutal equilibrium approach to calculate the driving force for the growth of both graphite and austenite phases. The growth kinetics of graphite also includes the effect of the density difference between iron and graphite. The model is applied to simulate the microstructural evolution of both hypoeutectic and hypereutectic SG irons. The simulated microstructures, cooling curve and graphite nodule sizes at various cooling rates compare reasonably well with the experimental data, demonstrating the quantitative capabilities of the proposed model. The simulation results reveal some dynamic features of the divorced eutectic solidification, such as the interactive and competitive growth between austenite dendrites and graphite nodules, and the graphite growth controlled by carbon diffusion through the solid austenite shell.