Effects of TiC particles on microstructure, deformation mechanisms and tribological behavior of AZ31B Mg composites fabricated by additive friction stir deposition

Additive friction stir deposition (AFSD) has emerged as a solid-state additive manufacturing process for fabricating lightweight metallic components, however, controlling particle content to achieve a balanced combination of strength, ductility, and wear resistance remains a critical manufacturing challenge for particle-reinforced magnesium (Mg) composites. In this study, TiC-reinforced AZ31B Mg composites with TiC contents ranging from 0 to 10 vol.% were fabricated by AFSD to elucidate the microstructure-property relationships governed by particle content regulation. The results show that the severe plastic deformation and thermo-mechanical coupling inherent to AFSD promote the formation of refined equiaxed Mg grains, while the introduction of TiC particles further suppresses grain growth and weakens basal texture through particle-stimulated grain refinement. Tensile properties exhibit a process-dependent strength-ductility trade-off, with an optimal processing window identified at 5 vol.% TiC, yielding an ultimate tensile strength of 298.1 ± 11.8 MPa and an elongation of 10.7 ± 2.8%. EBSD and TEM analyses reveal that deformation is dominated by basal slip, while TiC particles modify local strain accommodation by activating tensile twinning and limited non-basal slip near particle-matrix interfaces and grain boundaries. Tribological tests indicate that AFSD processing combined with moderate TiC addition significantly enhances wear resistance, accompanied by a transition in the dominant wear mechanism from oxidation wear to abrasive wear. In contrast, excessive TiC content leads to particle clustering, strain localization, and delamination wear, resulting in deteriorated wear performance. These results demonstrate that particle content regulation provides an effective route for process optimization in AFSD Mg matrix composites, offering practical guidance for manufacturing lightweight components with improved structural and tribological performance.