Enhanced mechanical properties and thermal conductivity of Ti-reinforced Mg–9Gd–3Y–0.5Zr composite via heterogeneous bimodal structure and nanoscale precipitation

Hard-plate rolling (HPR) after extrusion was employed to prepare Ti-reinforced Mg–9Gd–3Y–0.5Zr (VW93) composites. The composite exhibited optimal comprehensive performance with an ultimate tensile strength of 501 MPa, a yield strength of 448 MPa, an elongation of 8.5%, and a thermal conductivity ( λ ) of 63.1 W m −1 K −1 after aging treatment. The thermal conductivity represents a 52.7% improvement over the VW93 alloy and an 80.8% increase compared to the extrusion state. HPR deformation led to a distinct heterogeneous bimodal microstructure in both the aged composite and alloy, characterized by the coexistence of dynamically recrystallized (DRX) grained hard zones and unDRX grained soft zones. During aging, the primary strengthening mechanism involved participation of nano-Mg 5 (Gd, Y) and nano-β′ phases in hindering the dislocation slip, and superior hetero-deformation-induced strengthening from the deformable Ti particles promoted the nucleation of DRX grains and restricted grain growth. Furthermore, the precipitation of nano-Mg 5 (Gd, Y) and nano-β′ phases decreased the matrix solute content, and deformable Ti particles alleviated lattice distortion, significantly enhancing thermal conductivity. Therefore, the synergistic coupling between Ti-particle-stimulated heterogeneous structure and precipitation effects provides new insights for developing high-performance magnesium matrix composites with balanced mechanical properties and thermal conductivity.