Microstructure and mechanical properties of TiB–TiB2 ceramic matrix composites fabricated by spark plasma sintering

TiB–TiB2 ceramic matrix composites were synthesized by spark plasma sintering (SPS) process using Ti and TiB2 powders. The microstructure, mechanical properties, and the densification behavior of the in situ synthesized TiB–TiB2 composites were investigated. The effect of the addition of Ti on the microstructure and the reaction products of the composites were discussed. The results indicated that the composite synthesized from the mixtures containing 5 wt.% Ti and 95 wt.% TiB2 at 1650 °C had the highest relative density of 99.4% along with flexural strength of 534 MPa and fracture toughness of 6.19 MPa m1/2. However, when the weight content of Ti in the mixtures exceeded 15%, the mechanical properties of the in situ synthesized TiB–TiB2 composites decreased due to the extensive formation of the TiB secondary phase at the TiB2 grain boundaries and the rapid grain growth of the TiB and TiB2 phases.