Effect of zirconium on microstructures and mechanical properties of squeeze cast Al–5.0Cu–0.4Mn–0.1Ti–0.1RE alloy

Abstract

Al–5.0Cu–0.4Mn alloys with different Zr additions have been prepared by direct squeeze casting. The effects of Zr on microstructures and mechanical properties of the as-cast and T6 heat-treated alloys were investigated by tensile test, optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the optimal tensile property of the as-cast alloy occurs at the Zr content of 0.15% (mass fraction) due to the “Zr poisoning” action and the appearance of bulky primary Al3Zr, which decreases the grain refinement strengthening effect of the as-cast alloy. The peak values of ultimate tensile strength and yield strength of the T6 alloy occur at the Zr content of 0.25%, and that of the elongation occurs at Zr content of 0.05%. This is mainly attributed to the strengthening effect of dispersed precipitation of Al3Zr and θ’ phases. The optimal mechanical properties of T6 heat-treated alloy are the tensile strength of 429 MPa, the yield strength of 327 MPa and the elongation of 18%, respectively when the squeeze pressure is 100 MPa and Zr content is 0.25%.