Optimizing strength and ductility of Al–7Si–0.4 Mg foundry alloy: Role of Cu and Sc addition

Abstract The roles of Cu and Sc addition on optimizing strength and ductility of Al–7Si–0.4 Mg foundry alloy (A356) were systematically investigated in the present work. The results showed that 1.5 wt% Cu addition to A356 alloy causes a remarkable promotion coupled with significant expense of elongation, and addition of 0.6 wt% Sc slightly enhanced the strength and ductility of A356 alloy. The optimized tensile properties can be achieved in A356 alloy with 1.5 wt% Cu and 0.6 wt% Sc synergistic addition, which was indicated by the calculated quality index (QT). The ultimate tensile strength (UTS), yield strength (YS) and total elongation (TE) of the alloy with Cu and Sc additions are 349.7Mpa, 236.9 MPa and 14.6%, respectively. The improvement of tensile properties was attributed to refinement of grains and secondary dendrite arm spacing (SDAS), modification of eutectic Si, precipitation of nano-sized Al3Sc and θ′-Al2Cu dispersoids. The weibull analysis of tensile data were also systemically discussed in this study.