Effects of Fe, Mg Contents and Heat Treatment on Microstructure and Tensile Properties of Die-casted Al-Si Alloys

Al-Si alloys with different contents of Fe and Mg were prepared by conventional and vacuume die casting processes, and then solid solution and aging heat treatment of the alloys were completed. The effects of Fe and Mn contents on microstructure and tensile properties of coventional die-casted alloys, and heat treatment on tensile properties and fracture of vacuume die-casted alloys were studied. The results show that when mass fraction of Mg in Al-Si alloys was 0.55%, mass fraction of Fe must not exceed 0.60%, otherwise flaky Al9Fe2Si2 phase would generate easily because of excess Fe content, this phase was bad to mechanical properties of the alloys. Adding Mg could make flaky Al9Fe2Si2 phase turned to Al8Mg3FeSi6 phase, which could remove harmful effects of Fe to some extent and improve tensile properties of the alloys. Tensile strength of the die-casted alloys increased by 12% under vacuume die-casting condition, and heat treatment could make the tensile strength of vacuum die-casted alloys increase by 26.17%.