Mechanical properties and in-situ toughening mechanism of pressurelessly densified ZrB2-TiB2 ceramic composites

Refractory metal diboride ceramics are promising materials for various high temperature applications. In this work, systematic studies were conducted on the mechanical properties, including the strength at elevated temperatures, of in-situ toughened ZrB2-TiB2 ceramic composites that were prepared via pressureless sintering at 2100 °C for 2 h. Linear shrinkage and open porosity measurements indicated that the composites were fully densified. Microstructural observations revealed intergranular cracking behaviour. Thermal residual stress along with elongated SiC platelets contributed to the improvement in toughness. The toughness was strongly affected by the ZrB2 grain size. The high temperature degradation of the flexural strength was attributed to the presence of oxide species.