The application of magnesium alloys is hindered by the inherent contradiction between mechanical performance and thermal conductivity. Achieving simultaneous enhancement of both properties is crucial for broadening their applications. In this study, Mg-5Zn-xCu-0.5Zr (x = 0, 0.5, 1, 2) alloys were fabricated using semi-solid rheo-diecasting (RDC). The microstructure was characterized via OM, SEM, XRD, TEM and EBSD, and its influence on mechanical properties and thermal conductivity was analyzed. The results show that adding Cu refines the grain size, induces the formation of the MgZnCu phase, and reduces solidification shrinkage defects. The RDC Mg-5Zn-xCu-0.5Zr alloy features a heterogeneous microstructure comprising primary α-Mg (α1) with low solute content, secondary α-Mg (α2) with high solute atom content, and intergranular second phases. This heterogeneous structure synergistically enhances both mechanical properties and thermal conductivity. Specifically, α1 grains and the MgZnCu phase reduce lattice distortion, thereby improving thermal conductivity, while α2 generates more dislocations during tensile deformation, contributing to enhanced mechanical properties. Additionally, a small amount of MgZnCu phase contributes to simultaneous improvements in both properties. However, excessive MgZnCu phase can lead to stress concentration due to dislocation pile-up, causing fracture and degrading mechanical properties. Among the alloys studied, the Mg-5Zn-1Cu-0.5Zr alloy exhibits the best combination of mechanical and thermal properties, with a tensile strength of 221 MPa, yield strength of 109 MPa, elongation of 5.72%, and thermal conductivity of 113.8 W/(m·K). This demonstrates the successful simultaneous enhancement of both mechanical and thermal properties in magnesium alloys.

Through the innovative integration of semi-solid rheo-casting with extrusion shear process, the short-process fabrication of low-alloyed wrought Mg-2Zn-1Mn alloy is achieved in this study. Uniaxial tensile testing of low-temperature extrusion shear specimens (200 ℃) demonstrates the exceptional strength-ductility synergy, yield strength of 277 MPa, yield strength ratio of 0.95, and elongation of 24 %. Microstructural observations reveal the mechanisms underlying its high strength-plasticity synergy at room temperature. This study investigates the effects of different temperature gradients on the microstructure by analyzing experiments conducted at three temperatures: 300 ℃, 250 ℃, and 200 ℃. Ultimately, the formation mechanism of the bimodal microstructure obtained at 200 ℃ is elucidated. The distinctive crystallographic texture oriented at 34° relative to the loading axis direction effectively mitigates stress concentration by inducing the synergistic activation of multiple slip systems. Furthermore, the transition trends of different slip systems and texture evolution during tensile deformation are validated through Visco-Plastic Self-Consistent (VPSC) simulations and corroborated by microstructural analysis. With geometrically necessary dislocation (GND) density (4.28 × 10¹⁵ m^-2) and pyramidal slip activation (~45%). This study has successfully broken through the bottleneck of strength-ductility trade-off in magnesium alloys, providing theoretical support for the development of high-reliability magnesium alloys.