In-situ synthesis and mechanical properties of (TiB²⁺TiC)/Ti₃SiC₂ composites

Based on thermodynamic analysis, (TiB²⁺TiC)/Ti₃SiC₂ composite ceramics were in-situ prepared by hot-pressing with TiH₂, Si, graphite and B₄C powders as raw materials. The phase composition and microstructure of the materials were characterized by XRD, SEM and TEM. Effects of sintering temperature on phase composition, sintering performance, microstructure and mechanical properties were investigated. The results indicate that fully densified (TiB²⁺TiC)/Ti₃SiC₂ composite ceramics could be obtained after sintered at 1400-1600°C. With the increase of sintering temperature, the bending strength, fracture toughness and Vickers hardness of the composite increase gradually. The materials sintered at 1500-1600°C show optimized microstructure and consequently excellent mechanical properties, i.e., bending strength of above 700MPa, fracture toughness of above 9MPa · m^1/2 and Vickers hardness of 7.33-8.31GPa. As reinforcing agents, columnar TiB₂ grains and equiaxed TiC grains, were incorporated by in-situ reaction during hot-pressing process to increase the strength and toughness of Ti₃SiC₂ matrix dramatically by the synergistic action of the mechanisms such as particulate reinforcement, crack deflection, grain's pull-out and fine-grain toughening.