<I>In-situ</I> Synthesis and Mechanical Properties of (TiB<SUB>2</SUB>+TiC)/Ti<SUB>3</SUB>SiC<SUB>2</SUB> 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℃.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℃ show optimized microstructure and consequently excellent mechanical properties,i.e.,bending strength of above 700MPa,fracture toughness of above 9MPa·m1/2 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.