Growth Mechanism of Eutectic Si in Super-Gravity Solidified Al-Si Alloy during Annealing

Herein, we report that the influence of annealing time on the microstructure and mechanical properties of Al-14.5Si alloys solidified under a super-gravity field. The results indicate that the coarsening of metastable eutectic Si and formation of precipitated Si could be observed at the early stage of annealing. A slight increase in yield strength and tensile strength could be observed in the sample annealed for 0.25 h, which can be ascribed to the formation of precipitated Si with limited size during the early stage of annealing. The intensified diffusion of Si atoms during annealing led to the coarsening and coalescence of the eutectic Si, as well as the coarsening of precipitated Si with further extension of the annealing time.