This study investigated the influence of heat treatment on the characteristics of friction stir processed (FSP) WE43 magnesium (Mg) alloy reinforced with titanium carbide (TiC) nanoparticles. While FSP effectively distributes reinforcement particles and refines microstructure, the combined effects of FSP parameters and post-processing heat treatment on WE43/TiC surface composites remain inadequately explored. WE43 substrates reinforced with TiC nanoparticles (45–65 nm) were processed using FSP at varying tool rotations (800–1700 rev/min) and feed rates (30–60 mm/min), followed by T5 aging treatment at 250 \(^\circ{\rm C}\) for 16 h. Heat treatment significantly enhanced the surface hardness of WE43/TiC composites by 9.6%, achieving a maximum hardness of 165.7 HV0.3 at optimal processing conditions (1700 rev/min, 60 mm/min). The thermal treatment induced grain refinement, reducing grain size by 10–11% to 1.8 \(\upmu\) m in the composite matrix. Wear resistance demonstrated remarkable improvement, with heat-treated WE43/TiC composites exhibiting 72% lower wear rate (0.014 mm3/m) compared to as-received WE43 substrates. Corrosion resistance was substantially enhanced, showing 79.7% improvement with corrosion current density reduced to 1.4 ± 0.7 × 10−5 A/cm2. The uniform dispersion of TiC nanoparticles, evolution of fine grain microstructure after the dissolution of \(\beta\) -phase precipitates (Mg24Y5 and related rare-earth containing intermetallic compounds) by heat treatment, and formation of protective oxide layers contributed to these enhanced properties. The synergistic effects of FSP and heat treatment provide an effective approach for developing high-performance Mg-based surface composites for advanced engineering applications.
