Fabrication of HEA particle-reinforced AZ91 magnesium matrix composites via WAAM-FSP hybrid process: Microstructural regulation and performance optimization

Magnesium matrix composites (MMCs) have attracted increasing attention due to their potential for achieving superior strength-ductility synergy; however, the fabrication of MMCs with homogeneous particle distribution and optimized properties remains challenging. In this study, (AlTi) 0.5 FeCoCrNi high-entropy alloy (HEA) particle-reinforced AZ91 MMCs were fabricated via a wire arc additive manufacturing (WAAM)-friction stir processing (FSP) hybrid process, and the effects of FSP and HEA particles (HEA P ) on the macroscopic formability, microstructure, mechanical properties and tribological behaviors were systematically investigated. At a fixed FSP traverse speed of 40 mm/min, 500–600 r/min was identified as the optimal rotational speed range, ensuring defect-free formability and uniform HEA P dispersion. The HEA P /Mg interface exhibited excellent bonding with an elemental transition zone of approximately 1.9 µm in thickness, where localized Al enrichment was closely associated with the formation of interfacial β-Mg 17 Al 12 precipitates. FSP and HEA P synergistically regulated the microstructure by inducing grain refinement, modifying texture and alleviating lattice distortion. The MMCs achieved a significant strength-ductility synergy, with the ultimate tensile strength, yield strength and elongation reaching 260.39 MPa, 112.56 MPa and 14.80%, corresponding to increases of 41.50%, 19.50% and 179.25%, respectively, compared with the as-deposited WAAM-AZ91 alloy, mainly due to coefficient of thermal expansion mismatch and grain refinement strengthening. Moreover, the MMCs exhibited improved wear resistance, with the wear weight loss reduced from 2.8 mg to 1.0–1.5 mg, despite an increased coefficient of friction. This study provides an effective strategy for fabricating high-performance MMCs with improved strength-ductility synergy and wear resistance.