Self-healing ability and full strength recovery at medium temperatures of low content titanium carbide/alumina composites

Crack self-healing ability at high temperatures (>1000 °C) has been reported in alumina (Al2O3) composites dispersed with silicon carbide. For lower self-healing temperature ranges, such as 600–800 °C, titanium carbide (TiC) has been considered as a promising healing agent. However, no investigation has been conducted on Al2O3 containing a low volume (<15 vol %) of TiC. In this study, Al2O3 composites dispersed with 10 vol % of micro/nano TiC particles were prepared by a hot pressing method, then the mechanical properties and the self-healing ability were investigated. The composites were pre-cracked on the surface by a Vickers hardness tester, then annealed at 400 and 700 °C for 1–3 h to demonstrate the self-healing ability. Scanning electron microscope (SEM) observations and bending strength tests confirmed that the cracks were almost healed after annealing at 700 °C for 3 h. Characterizations by adsorption–desorption isotherm, thermogravimetry, and X-ray diffraction have pointed out that the size of TiC healing particles plays an important role on the healing rate and strength recovery of the composites.