A high performance Mg-Al-Ca alloy processed by high pressure die casting: Microstructure, mechanical properties and thermal conductivity

The demand for high-performance magnesium alloys, including high strength, high thermal conductivity, and good heat resistance, is growing rapidly in practical applications. Here, we report a high performance Mg-7Al-3Ca (AX73, wt.%) alloy with high strength, good thermal conductivity, and acceptable heat resistance via the high-pressure die casting (HPDC) method. Compared to the commonly used Mg-4Al-4RE (AE44) and Mg-9Al-1Zn-0.25Mn (AZ91D), the HPDC AX73 exhibited a much higher yield strength (YS) at room temperature (RT) and 175 C. The high YS was attributed to the combinations of fine-grain strengthening, second phase strengthening from numerous Al2Ca eutectic phases, and solid solution strengthening from Al solutes. After the aging treatment, the room-temperature YS of AX73 alloy was further improved from 184 MPa to 196 MPa due to fine Al2Ca precipitation. Since the existence of Ca obviously reduced the Al solutes in the alpha-Mg matrix, the AX73 and AX73 aged alloys possessed reasonable thermal conductivity of 67 and 68.5 W(m.K)- 1, respectively.