This paper presents two and three dimensional cellular automaton (CA) based models and derived coupling models to simulate micro-scale microstructure evolution during alloy solidification. The models adopt a local solutal equilibrium approach to calculate the kinetics of the solid/liquid (SL) interface evolution, which allows the reasonable calculation of crystal growth from the initial unstable stage to the steady-state stage without the need of a kinetic parameter. Dendrite morphologies with various crystallographic orientations and well developed side branches in two and three dimensions can be successfully simulated by the proposed models. In conjunction with the lattice Boltzmann method (LBM), adopted for numerically solving fluid flow and solutal transport, a coupling model was derived to simulate the solutal dendrite growth in the presence of melt convection. The 2D model was extended to the multiphase system for the simulation of divorced eutectic solidification of spheroidal graphite (SG) cast iron. The quantitative capabilities of the models are addressed by comparing simulations to analytical predictions and experimental data.KEY WORDS: solidification; microstructure simulation; cellular automaton; lattice Boltzmann method.
1851© 2010 ISIJ Review and trapping rules for new interface cells. The quantitative capabilities of the model were well addressed by validation of the simulation results with experimental data and the Lipton-Glicksman-Kurz (LGK) theory.Lee and co-workers 14,15) developed a CA-FD model in which the growth velocity is also determined by solving the solute conservation equation subject to the boundary conditions at the SL interface. The model adopts a modified decentered-square growth algorithm to generate various crystallographic orientations. Recently, the model was further developed by incorporating the solution of the NavierStokes equations to simulate the dendritic solidification under natural and forced convection in two and three dimensions.16)The diffusion-controlled CA models [10][11][12][13][14][15][16] with the assumption of solute conservation at the moving SL interface mentioned above have the merit of allowing the simulation of dendrite growth without the need of introducing a kinetic coefficient. Since the condition of solute conservation is only satisfied for steady-state growth, those CA models fail to reasonably calculate the growth velocity of the interface points undergoing unstable growth.Building on an earlier meso-scale CA model, Zhu and Hong developed a micro-scale modified CA (MCA) model by incorporating the effects of the solute and the curvature undercoolings on the equilibrium temperature at the SL interface. The model was applied to simulate single and multi-dendritic growth in two and three dimensions, 17,18) non-dendritic and globular microstructures formed in semisolid process, 19) dendritic growth in the presence of forced melt convection, 20,21) and microstructure formation in regular and irregular eutectic alloys. 22,23) The model was also extended t...