Evolution mechanisms of high temperature mechanical properties and microstructures of Al₂O₃/SiC_w/TiC_n nanocomposite materials

The addition of nanoparticles can greatly improve the mechanical properties of ceramic materials at room temperature, but the research on the toughening and strengthening effect of nanoparticles at high temperature is less reported. In this paper, the evolution law and evolution mechanisms of the mechanical properties including Vickers hardness, fracture toughness and flexural strength as well as elastic modulus of TiC nanoparticles dispersed Al₂O₃/SiC_w ceramic materials (Al₂O₃/SiC_w/TiC_n) at high temperature (up to 1200 °C) were meticulously investigated compared with those of Al₂O₃/SiC_w. The results showed that the Vickers hardness and fracture toughness of Al₂O₃/SiC_w/TiC_n were higher than those of Al₂O₃/SiC_w ceramic materials at both room and elevated temperature. Although the flexural strength of the Al₂O₃/SiC_w ceramic materials was improved by the addition of nanoparticles at room temperature, the intergranular fracture tended to occur along the refined matrix grains at high temperature, resulting in lower high temperature flexural strength of Al₂O₃/SiC_w/TiC_n composite. The Vickers hardness of both the two composites decreased with increasing temperature (20–1000 °C). At 1000 °C, the hot hardness of the composite with TiC nanoparticles addition was still maintained 68.4% of hardness at room temperature. The fracture toughness of the two composites decreased rapidly from 900 °C above but increased to a peak at 1200 °C. The addition of TiC nanoparticles played a positive role for improving the hot hardness and high temperature fracture toughness, but was not conducive to the high temperature flexural strength.