Numerical simulation on solute partition and solid fraction evolution in solidification of Al-Cu-Mg alloys

By coupling micro-scale solidification model with CALPHAD technology, the variation of solute partition coefficients for elements Cu and Mg was numerically studied during dendritic solidification process of Al-Cu-Mg alloys. By taking alloy Al-3.9%Cu-0.9%Mg as an example, the variation of solute partition coefficients as the function of solid volume fraction was obtained. It was found that the partition coefficients changed greatly during solidification process and strongly depended on the cooling rate. Furthermore, the evolution of solid volume fraction, i.e., f _s-T curve, for Al-15.0%Cu-4.0% Mg alloy was also quantitatively predicted at different cooling rates. With the increase of cooling rate, the f _s-T curve shifts to the side of low 4 values at the same temperature, and the volume fraction of the non-equilibrium eutectic increases. The numerical results at the cooling rate of 6 K/min are well in agreement with the DTA analysis results.