Effects of Precursor Alloy Temperatures and Gate Angle on the Microstructure of an Al–Si Alloy Prepared by Controlled Diffusion Solidification

The effects of temperature difference between two precursor melts and angle between two gates for pouring the two melts on the microstructure of controlled-diffusion-solidified Al–8Si alloy were investigated by simulation and experiment. The simulation results showed that only the temperature difference was higher than 50 K, the nucleation rate during mixing could reach a critical value (corresponding to ~30% of solidified mesh number in simulations), and thus, a microstructure with small and spheroidal primary grains was obtained. Increasing the gate angle was beneficial for achieving a mixed melt with smaller and more alloy 1 pockets, and thereby was helpful for increasing nucleation rate and obtaining an ideal nondendritic microstructure. The subsequent experiment results confirmed these simulation results. When the temperature difference and gate angle were at 80 K and 140° respectively, an Al–8Si casting with grain size of 52.0 μm and a shape factor of 1.40 was achieved.