Preparation of in-situ (TiB₂+TiC)/Ti₃SiC₂ composite ceramics by hot-pressing

(TiB₂+TiC)/Ti₃SiC₂ composite ceramics were prepared by in-situ hot-pressing in Ar atmosphere. The phases and microstructures of the materials were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The effects of sintering temperature on the phases, sintering performance, microstructures and mechanical properties of the ceramics were investigated. The results show that with the increase of sintering temperature, the reaction among raw materials proceeds completely and the density, bending strength and fracture toughness of the ceramics increase significantly. Fully densified in situ (TiB₂+TiC)/Ti₃SiC₂ composite ceramic with well-developed and optimized microstructure could be obtained when sintered at 1500°C, in which laminated Ti₃SiC₂ grains, columnar TiB₂ grains and equiaxed TiC grains were observed clearly. Moreover, owing to the superiority of in situ reaction, the reinforcing agents of TiB₂ and TiC have small grain size and the grain boundaries are clear and clean. The composite ceramic shows the maximum bending strength (741 MPa), fracture toughness (10.12 MPa · m^1/2) and Vickers hardness (9.65 GPa). When sintering temperature was higher than 1550°C, the density and mechanical properties of the ceramics decrease gradually as a result of the decomposition of Ti3SiC2 matrix.