Fabrication and improved properties of ZrC-SiC-ZrB2 ceramics by ultra-high pressure sintering

ZrC-SiC-ZrB 2 ceramics were prepared via ultra-high pressure sintering under 15 GPa at 1200 °C. The densification mechanism, microstructures, and properties of the prepared ceramics were investigated. The sintered ceramics with ZrB 2 content of 15 vol   % showed the improved comprehensive mechanical properties, including Vickers hardness of 26.6 GPa, Young's modulus of 469.1 GPa, and fracture toughness of 5.0 MPa·m 1/2 , which was 86.7   % higher than that of pure ZrC ceramics. In the sintered sample, the ultra-high pressure induced new microstructure, such as L-C lock in ZrC phase, stacking faults and nanotwins in SiC phase, and severe lattice distortion in ZrB 2 phase, jointly contributed to the improvement in Vickers hardness. Deflection and bridging during crack propagation were ascribed to the uniform combination of various phases.