Thermal conductivity and mechanical performance of Cu microalloying as-cast ZK60 alloy

Copper (Cu) was introduced in the ZK60 alloy as a microalloying element. The microstructure, thermal conductivity, and mechanical performance of ZK60-xCu (x = 0, 0.2 wt%, 0.5 wt%, 1 wt%) alloys were systematically investigated to develop new as-cast magnesium alloys with high thermal conductivity and excellent mechanical performance. The results indicated that the Cu can refine the grains ZK60 alloy of owing to the pinning effect of precipitated MgZnCu phase at grain boundaries. The addition of Cu significantly improved the thermal conductivity of the ZK60 alloy. When 0.5 wt% Cu is added, the thermal conductivity reaches the highest value of 128.3 W/(m center dot K). This is due to the fact that the formation of the MgZnCu phase consumes a large amount of solid solution Zn and Cu and provides the alloy with a large number of free electrons due to its thermal stability. In addition, the optimum strength-toughness combination was also achieved in the ZK60-0.5Cu alloy (193.2 MPa for UTS, 98.3 MPa for YS, and 16.8 % EL). This is mostly attributed to the synergistic effect of fine grain strengthening combined with precipitation strengthening. This satisfies the need to develop novel as-cast magnesium alloys with excellent mechanical and thermal conductivity properties.