Effect of Annealing on Microstructure and Mechanical Properties of Al–18Si Alloy Cast by Melt Quenching

Abstract

In this study, an experimental device was designed to conduct melt quenching of Al–18Si alloy. The effect of annealing treatment on microstructure and mechanical properties of Al–18Si alloy cast by melt quenching was studied. The results showed that the microstructure of Al–18Si alloy cast by melt quenching was transformed into a pseudo-eutectic microstructure. With the increasing annealing temperature, the dissolution and diffusion rates of the eutectic silicon phase increased, and with the extension of holding time, eutectic silicon tended to spherulite. The best spherulite microstructure was obtained by annealing the alloy at 580°C or 40 min, and the silicon phase surface shape factor (φ) in the microstructure was 0.8. After annealing at 580°C for 40 min, the maximum impact toughness (σ_b) and elongation (δ) of Al–18Si alloy cast by melt quenching was 99.0 J/cm² and 13.6%, respectively. Compared with the unannealed Al–18Si alloy cast by melt quenching, the impact toughness and elongation of the annealed alloy increased by 239.0 and 112.5%, respectively.