Preparing B4C-SiC-TiB2 composites via reactive pressureless sintering with B4C and TiSi2 as raw materials

Abstract

B4C-SiC-TiB2 composites with high densification were fabricated by in-situ reactive pressureless sintering with B4C and TiSi2 as the raw materials. The phase composition, relative density, microstructure, mechanical properties and fracture mode of the fabricated composites were investigated. Besides, the reaction mechanism and toughening mechanism were studied. The results indicate that TiSi2 can react with B4C and C to form TiB2 and SiC below 1400 ℃. A multi-component eutectic liquid phase is formed in the sintering process due to the presence of impurities, which enhances the densification. The relative density, hardness and fracture toughness of the composites sintered at 2200 ℃ with 30 wt% TiSi2 are 97.2%, 27.9 GPa and 3.8 MPa m1/2, respectively. The fracture mode of different-size TiB2 phase in the composites is the coexistence of intergranular and transgranular fracture according to the crack propagation path and the observation of fracture surface. The toughening effect is owing to the high-toughness second phase (SiC), the coexistence of intergranular and transgranular fracture of TiB2 and the stepped fracture in TiB2 phase.