Effect of heat treatment on the microstructure and high-temperature mechanical properties of in situ hybrid (TiB+TiC+Ti₃Si)/TC4 composites

In this work, novel precursor-derived (TiB+TiC+Ti₃Si)/TC4 composites were successfully fabricated with uniform distribution of hybrid reinforcements. To further enhance high-temperature performance, heat treatments were conducted in the (α+β) two-phase region (940 °C, 980 °C, and 1020 °C) followed by aging at 600 °C and 650 °C. The microstructural evolution and mechanical properties at 600 °C were systematically characterized. Results show that heat treatment refines the α and β phases, promotes precipitation of silicides at α/β phase boundaries, and improves load transfer from matrix to reinforcement. The composite treated at 1020 °C/40 min (WQ) + 600 °C/6 h (AC) exhibits the best high-temperature tensile strength of 708 MPa at 600 °C, which is 119 MPa higher than that of the as-forged composite. The enhancement is attributed to solid-solution strengthening, grain refinement, dispersion strengthening by nano-sized silicides, and improved interfacial bonding. This study provides a theoretical basis for microstructural design and high-temperature performance optimization of hybrid-reinforced titanium matrix composites for applications above 600 °C.