Densification, microstructure and mechanical properties of ZrB2–SiCw ceramic composites

ZrB2–SiCw composites were prepared through hot-pressing at a low temperature of 1800 °C, and Al2O3 plus Y2O3 were added as sintering aids. Analysis revealed that additives may react with impurities (i.e. surface oxygen impurities and residual metallic impurities) to form a transient liquid phase, thus promote the sintering and densification of ZrB2–SiCw composites. The content of additives was found to have a significant influence on the sinterability, microstructure and mechanical properties of ZrB2–SiCw composites. ZrB2–SiCw composite prepared with a small amount of additives (3 vol.%) provided the optimal combination of microstructure (relative density of 98.3%) and excellent properties, including flexural strength of 783 MPa and fracture toughness of 6.7 MPa m1/2. With further addition of additives, SiC whiskers were inclined to gather together and be enveloped by excessive liquids to form core-rim-like structures, which lead to little decrease in mechanical properties.