Pressureless liquid-phase sintering of B4C with MoSi2 as a sintering aid

Abstract Pressureless sintering of B 4 C with MoSi 2 (5–30 wt%) as a sintering aid was carried out at 1600–2260 °C in vacuum. The phase compositions, relative density, microstructures and mechanical properties of the obtained ceramic composites were investigated. Results indicate that MoSi 2 can react with B 4 C to in-situ form Mo 2 B 5 and SiC below 1600 °C. Mo 2 B 5 will gradually transform to MoB 2 with the further increasing temperature. Liquid-phase sintering of B4C is realized at about 2150 °C and the formed liquid phase fills the pores in the matrix, enhancing the densification of the composites. The relative density, fracture toughness and hardness of the samples with 30 wt% MoSi 2 sintered at 2260 °C reach 96.5%, 3.98 MPa m 1/2 and 28.1 GPa, respectively. The high-toughness second phases and the coexistence of transgranular and intergranular fracture have a synergistic effect on improving the overall fracture toughness of the ceramic composites.