Abstract: The development of magnesium (Mg) alloys with both high thermal conductivity and mechanical properties is critical for advanced thermal management applications, particularly in high-power 5 G base stations. However, conventional Mg alloys are inherently limited by a trade-off between these properties. In this study, the influence of thermomechanical processing, specifically extrusion temperature and ratio, on the microstructure, thermal conductivity, and mechanical performance of a Mg-3Zn-0.2Cu-0.2Ca-0.4Zr (wt%) alloy was systematically investigated. Characterization techniques, including OM, SEM, EBSD, TEM, and quasi-in situ EBSD, were employed to reveal the underlying mechanisms. Optimal property synergy was achieved at 285 °C with an extrusion ratio of 8:1, yielding a tensile strength of 344 MPa and thermal conductivity of 139 W/(K m), achieved through MgZn₂ dynamic precipitation that reduces matrix solute content. Thermal conductivity was found to be primarily controlled by solute redistribution and precipitation behavior. Furthermore, the increase and refinement of the second phase after solute redistribution and the refinement of the grain size achieved by regulating the extrusion parameters will lead to a significant enhancement of the mechanical properties. These findings provide a mechanistic basis for microstructural engineering of Mg alloys via thermomechanical processing, enabling the design of lightweight materials with enhanced thermal conductivity and mechanical properties.

Key words: Mg alloys, Thermal conductivity, Mechanical properties, Plastic deformation mechanisms