High strength, high thermal conductivity Mg–Zn–Ce alloys prepared by rapid solidification and hot extrusion

Developing magnesium alloys that simultaneously achieve high strength and high thermal conductivity remains a challenge due to the typical trade-off between these properties. In this paper, Mg-xZn-4Ce (x=2, 4, 6 wt.%, i.e., ZE24, ZE44 and ZE64) alloys were investigated by melt spinning rapid solidification combined with 350°C hot extrusion (RS-HE), aiming to develop novel high-strength, high-thermal-conductivity magnesium alloys.. The RS-HE process resulted in a unique microstructure consisting of an ultra-fine α-Mg matrix (∼1 μm), nanoscale ternary Mg-Zn-Ce phases ( ∼130 nm), and even finer Mg-Ce precipitates (∼30 nm). This refined microstructure led to an exceptional combination of properties: high thermal conductivity of 136.3, 131.2, and 122.8 W/(m·K), coupled with high yield strength of 473.8, 426.5, and 405.7 MPa for ZE24, ZE44, and ZE64, respectively. These values, particularly for the ZE24 alloy, surpass most previously reported high-performance magnesium alloys. Quantitative reinforcement mechanism analysis shows that the grain refinement and nanoscale second phases contribute more than 80% of the total yield strength, while the thermal conductivity loss attributable to them accounts for no more than 30% of the total thermal conductivity loss. In addition, compared with the cast alloy, the reduction of Zn solubility in the α-Mg matrix during hot extrusion can increase the thermal conductivity by 5∼6.8 W/(m·K) . This study demonstrates that the RS-HE strategy effectively breaks the traditional trade-off between strength and thermal conductivity. By refining microstructure, regulating nanoscale secondary phases, and controlling low solid solubility, it opens new avenues for designing advanced high-performance magnesium alloy materials.