In-Situ Synthesis of (W_P + TiC_P + TiB_W)/TA15 Hybrid-Reinforced Composites by Spark Plasma Sintering: Microstructure and Mechanical Properties

Titanium matrix composites (TMCs) have application prospects in the aerospace, military, and automobile sectors. In this paper, novel hybrid-reinforced TMCs with both high strength and ductility were fabricated by introducing tungsten particles (W_P) and in-situ synthesized ceramics (TiB_W + TiC_P) as combined reinforcements. Systematic multiscale microscopic analyses, thermodynamic calculations, and quasi-static tensile tests revealed the microstructures and synthesis mechanism of hybrid reinforcement clusters and their strengthening effect on the Ti-alloy matrix. In the TMCs, the hybrid reinforcements had a core-shell structure with W_P as the core and ceramic phases as the outer layer. The ceramic shell contains various phases such as TiC, TiB, W₂C, and WC formed by an in-situ synthesis reaction between B₄C, W, and Ti during sintering. The TMC with 3.2 vol pct hybrid reinforcements demonstrated the best mechanical properties with a yield strength of 896.39 MPa, ultimate tensile strength of 1081.23 MPa, and fracture strain of 11.1 pct. As the W_P content increased, the mechanical properties of the TMCs gradually deteriorated due to reinforcement agglomeration. The higher strength of TMCs was attributed to various strengthening mechanisms. When the W_P content increased, the strength increase caused by grain refinement was weakened, but the contributions of dislocation multiplication and load transfer were enhanced because the reinforcement clusters were larger and more continuous. The “filling” behavior of W_P eliminated micropores caused by the Kirkendall effect during the in-situ reaction between B₄C and Ti, which improved the density and ductility of hybrid-reinforced TMCs.