Microstructures and mechanical properties of Ti3SiC2/TiC–Al2O3 composites synthesized by reactive hot pressing

Ti3SiC2/TiC–Al2O3 composites with different Al2O3 contents were fabricated by in-situ reaction and hot pressing sintering. Laminar Ti3SiC2 grains and granular Al2O3 grains were densely packed and tightly bonded, and cubic TiC grains presented in the surfaces of Ti3SiC2 grains. Al2O3 significantly restrained the grain growth of Ti3SiC2 matrix. The dispersed Al2O3 grains inclined to be pulled out, but Al2O3 aggregates inclined to be cut by the crack front at the crack surface. The flexural strength and fracture toughness first increased and then decreased with the increasing Al2O3 content. The composite with 20 wt% Al2O3 addition showed the highest flexural strength of 649 MPa and with 10 wt% Al2O3 addition showed the best fracture toughness of 7.15 MPa m1/2. The mechanism responsible for improved mechanical properties for Ti3SiC2/TiC–Al2O3 composites were the synergistic action of particulate dispersion reinforcement, fine-grain toughening, grain pullout, microcrack deflection, and lamella bending and slipping from three different kinds of grains.