Simulation of α-Al grain formation in high vacuum die-casting Al-Si-Mg alloys with multi-component quantitative cellular automaton method

Al-Si-Mg alloys are the most commonly used material in high vacuum die-casting (HVDC), in which the morphology and distribution of α-Al grains have important effect on mechanical properties. A multi-component quantitative cellular automaton (CA) model was developed to simulate the microstructure and microsegregation of HVDC Al-Si-Mg alloys with different Si contents (7% and 10%) and cooling rates during solidification. The grain number and average grain size with electron backscatter diffraction (EBSD) analysis were used to verify the simulation. The relationship between grain size and nucleation order as well as nuclei density was investigated and discussed. It is found that the growth of grains will be restrained in the location with higher nuclei density. The influence of composition and cooling rate on the solute transport reveals that for AlSi7Mg0.3 alloy the concentration of solute Mg in liquid is higher at the beginning of eutectic solidification. The comparison between simulation and experiment results shows that externally solidified crystals (ESCs) have a significant effect for samples with high cooling rate and narrow solidification interval.