Microstructure and mechanical properties of hot-pressed Al2O3–mullite–ZrO2–SiC composites

In this study, the effects of SiC content, sintering temperature and Al2O3/SiO2 ratio on the microstructure and mechanical properties of hot-pressed alumina–mullite–zirconia–silicon carbide (Al2O3–mullite–ZrO2–SiC) composite ceramics were investigated systematically. The research results indicate that the composite ceramics have excellent combined properties when SiC content is 20 vol% and sintering temperature is 1530 °C, with Vickers hardness, fracture toughness and flexural strength of 17.5 GPa, 12.3 MPa m1/2 and 970 MPa, respectively. The fracture toughness and flexural strength are higher than those of monolithic Al2O3 ceramics and Al2O3-based composites, which are fairly attributed to the refined microstructures of composites and the synergistic effects of crack deflection, pull-out, branching, and phase transformation toughening mechanisms induced by short columnar Al2O3 grains and SiC platelets formed in the ceramics, as well as the ZrO2 particles existed in the ceramics.