Hardness and Oxidation Resistance of In Situ Synthesized Multi-phase (TiB + TiC + Ti5Si3) Hybrid-Reinforced Ti555-Type Titanium Matrix Composites

In situ hybrid-reinforced Ti555 titanium matrix composites (TMCs) (TiB + TiC + Ti5Si3) were prepared by low-energy ball milling and discharge plasma sintering using Ti555 titanium alloy powder and B4Cp, SiCp, and CNT as the raw materials, and then solution and aging treatment were performed. The effects of the content and type of reactants on the microstructure, microhardness of phase composition, and high-temperature oxidation behavior of the composites were investigated under the addition of different contents of B4Cp and addition of SiCp or CNT. A hardness test shows that the hardness of the composite with a volume fraction of 3.5%B4Cp+1.5%CNT (1243.36 HV) is more than twice that of the matrix (539.21 HV). An XRD analysis shows that the oxidation phase is mainly composed of TiO2, Al2O3, and SiO2. Scanning electron microscopy (SEM) showed that the oxide layer (32 mu m) was denser than the matrix (56 mu m) in the composite with a volume fraction of 3.5%B4Cp + 1.5%SiCp at 800 degrees C for 100 h. The results show that the addition of B4Cp and CNT can effectively improve the hardness of TMCs, and the addition of B4Cp and SiCp can effectively improve the high-temperature oxidation resistance of TMCs.