In-situ particle-melt pool interactions in wire-powder-arc directed energy deposition of TiC/AZ91 composites: Trade-off between strength and wear resistance

Magnesium matrix composites (MMCs) have emerged as ideal candidate materials for lightweight structural applications due to their exceptional properties. However, conventional fabrication methods face significant challenges in efficiently producing complex components. In this study, TiC/AZ91 composites with controlled and uniformly distributed reinforcements were successfully fabricated using wire-powder-arc directed energy deposition (WPA-DED) technology. The effects of micron-sized TiC particles on droplet transfer, microstructure, mechanical properties, and wear behavior of the composites were systematically investigated. The results revealed that the incorporation of TiC particles modified the forces acting on the droplets and increased the melt pool viscosity, resulting in a decreased droplet transfer frequency. Interactions among the particles, the arc, and the molten pool facilitated a uniform dispersion of the reinforcements within the MMCs. A high dislocation density near TiC particles and TiC/Mg interfacial effects were observed to promote the precipitation of a refined β-Mg 17 Al 12 phase. With the addition of 5 vol% TiC, the ultimate tensile strength (238.2 MPa), yield strength (114.5 MPa), and elongation (8.2 %) decreased by 10.2 %, 6.7 %, and 1.1 %, respectively, compared to the as-deposited AZ91 alloy. In contrast, the coefficient of friction and the wear rate were reduced by approximately 13.3 % and 8 %, demonstrating significantly improved wear resistance. The dominant wear mechanisms of the composites were identified as abrasive wear, oxidation, and mild delamination.