Mechanical properties and oxidation resistance of Ti₃SiC₂/SiC composite synthesized by in situ displacement reaction of Si and TiC

Ti₃SiC₂/SiC composite has been synthesized by in situ displacement reaction of Si and TiC powders. Its relative density is >98%. Its Vickers hardness was measured to be 8.7 GPa. Its flexural strength and the fracture toughness were 505 MPa and 5.3 MPa·m^1/2, respectively. Scanning electron micrograph (SEM) and transmission electron micrograph (TEM) were used to observe the microstructure of the composite. Mechanisms for its high flexural strength and fracture toughness were discussed, respectively. The composite shows a better oxidation resistance than monolithic Ti₃SiC₂ at high temperatures. The oxidation layers were comprised of an outer layer with coarse TiO₂ grains and an inner layer with a mixture of fine-grained SiO₂ and TiO₂. Its weight gain is only about 7.9 mg/cm² at 1200 °C in air for 21 h. However, that of Ti₃SiC₂ is 30 mg/cm². The results suggested that the in situ formation of SiC improved its oxidation resistance.