Microstructure and mechanical properties of B4C–TiB2 composites prepared by reaction hot pressing using Ti3SiC2 as additive

B4C–TiB2 composites were fabricated via reaction hot pressing at 2100°C under a pressure of 25MPa, using B4C and Ti3SiC2 powders as raw materials. The phase transformations, microstructure and mechanical properties were investigated by XRD, TG–DTA, SEM, TEM and EDS. It is found that the SiC and TiB2 particles are homogenously dispersed in the B4C–TiB2 composites, where nano-sized TiB2 particles are mainly located within the B4C matrix grains, while the large-sized TiB2 particles at the matrix grains boundaries. Due to the pinning effect of SiC and TiB2 particles on B4C grain growth, the grain size of the composite is significantly reduced, leading to a great improvement of the mechanical properties. B4C–TiB2 composite prepared from B4C-10wt% Ti3SiC2 starting powder shows high flexural strength, fracture toughness and micro-hardness of 592MPa, 7.01MPam1/2 and 3163kg/mm2, respectively. Crack deflection and crack bridging are most likely the potential toughening mechanisms in the composites. Furthermore, according to the XRD and TG–DTA analysis, the possible reaction mechanisms leading to the in-situ formation of TiB2 were proposed.