Novel Ti3SiC2-(Ti, Zr)B2 toughened (Ti, Zr)C-based composites with enhanced mechanical properties fabricated by dual in situ reactions hot-pressing at low temperature

The fully dense Ti3SiC2-(Ti, Zr)B2 toughened (Ti, Zr)C-based composites were fabricated at 1400-1600°C for the first time by dual in situ reactions hot-pressing with TiC, ZrB2, and Si as the initial powders. The influence of ZrB2, Si content and sintering temperature on the microstructure and mechanical properties of the composite was reported. When 10 mol% ZrB2 was added, Si combined with residual TiC to form Ti3SiC2 and SiC. However, with the addition of ZrB2 increase to 20 mol% and 30 mol%, Si participated in the formation of ZrSi and was not enough to react with TiC to form Ti3SiC2. The low-temperature in situ reactions, multiphase coupling effects, and the pinning effect of nano-SiC refine the microstructure of the composites. There are specific crystal orientation relationships between (Zr, Ti)C and (Ti, Zr)B2, as well as between (Ti, Zr)C and SiC. The layered Ti3SiC2 and plate-like (Ti, Zr)B2 by dual in situ reactions effectively improve the fracture toughness of the composites. The 10ZB-15 possesses a highest fracture toughness of 6.1 MPa⋅m1/2. The 30ZB-16 has the good comprehensive mechanical properties. The fracture toughness, flexural strength, and hardness of 30ZB-16 is 5.6 MPa⋅m1/2, 679 MPa, and 26.4 GPa, respectively. The Ti3SiC2 and TiB2 formed during dual in situ reactions enables the composite to exhibit excellent oxidation resistance and wear resistance.