Optimization of heat treatment process of Al–Mg–Si cast alloys with Zn additions by simulation and experimental investigations

With increasing demands of the high strength and light weight suspension components from automotive industry, aluminum alloys with higher strength than traditional alloys must be developed. In order to meet this requirement for cast Al alloys, higher solute concentration than traditional A356 alloys is needed to enhance the solute and later precipitation strengthening effects. Considering Zn as one of the alloying elements with high solubility in Al, we investigate the effects of Zn addition and related heat treatment parameters on the mechanical properties of Al–Si–Mg alloys by using a combination of experimental and thermodynamic methods. With the addition of Zn, the yield strength (YS) and ultimate tensile strength (UTS) of Al–Si–Mg alloys are significantly improved by up to 52.2% and 8.5% compared with those without Zn additions. After a proper heat treatment, the YS and UTS of Al–Si–Mg–Zn alloys can be further increased by up to 35% and 28%, respectively, compared to the as-cast state. Based on the study, optimal heat treatment parameters for Al–Si–Mg alloys with different Zn contents are proposed.