Effect of hot deformation parameters on high thermal conductivity Mg-3Zn-0.2Cu-0.2Ca-0.4Zr alloy

The present work systematically investigates the influence of hot deformation parameters on the dynamic recrystallization (DRX) behavior, plastic deformation mechanisms, and thermal conductivity of a high-performance Mg-3Zn-0.2Cu-0.2Ca-0.4Zr alloy. The results demonstrate that increasing the deformation temperature from 200 °C to 350 °C transforms the dominant DRX mechanism from continuous dynamic recrystallization (CDRX) and twin-induced dynamic recrystallization (TDRX) to a combination of CDRX and discontinuous dynamic recrystallization (DDRX), accompanied by an increase in DRX fraction and grain coarsening from ultrafine grains to 3.14-10.99 μm. Meanwhile, the plastic deformation mechanism shifts from basal slip and twinning at 200 °C to the coordinated activation of multiple slip systems at 350 °C. A reduction in strain rate from 0.5 s -1 to 0.001 s -1 promotes grain growth and raises the DRX fraction but does not alter the fundamental DRX or deformation mechanisms. In terms of thermal conductivity, optimal values were achieved at 250 °C across all strain rates, attributed to sufficient solute atom precipitation and moderate second-phase density. Specifically, the volume fractions of Mg(Zn,Cu) 2 and Ca 2 Mg 6 Zn 3 phases decreased from 1.0432% and 1.0331% at 200 °C to 0.8580% and 0.9749% at 250 °C, respectively, mitigating electron scattering. At 200 °C, high-density precipitates and dislocations reduced electron mean free paths, deteriorating thermal conductivity. Lowering the strain rate enhanced thermal conductivity by promoting dislocation annihilation, grain growth, and complete solute precipitation. These findings provide quantitative insights into microstructure regulation for developing high-thermal-conductivity wrought Mg alloys.