A cellular automaton model for dendrite growth in magnesium alloy AZ91

A coupled cellular automaton (CA)-finite element (FE) model was developed to calculate dendrite growth during the solidification of hexagonal metals. The model solved the conservation equations of mass, energy and solutes in order to calculate the temperature field, solute concentration and the dendritic growth morphology. Validation of the model was performed by comparing the simulation results with experimental and computational data from previously published works, showing qualitatively good agreement in the dendritic morphology. Application to magnesium alloy AZ91 (approximated with the binary Mg-8.9 wt% Al) illustrates the difficulty of modeling dendrite growth in hexagonal systems, observed as deviations in the growth direction caused by mesh-induced anisotropy. The model was applied to the simulation of small specimens with equiaxed grain growth and columnar grain growth in directional solidification. The influences of cooling rate, mesh size and kinetic parameters such as surface tension and anisotropy coefficient on the grain morphology were also discussed.