Self-healing behavior of Ti₂AlC at a low oxygen partial pressure

Ti₂AlC, a MAX phase ceramic, has an attractive self-healing ability to restore performance via the oxidation-induced crack healing mechanism upon healing at high temperatures in air (high oxygen partial pressures). However, such healing ability to repair damages in vacuum or low oxygen partial pressure conditions remains unknown. Here, we report on the self-healing behavior of Ti₂AlC at a low oxygen partial pressure of about 1 Pa. The experimental results showed that the strength recovery depends on both healing temperature and time. After healing at 1400 ℃ for 1–4 h, the healed samples exhibited the recovered strengths even exceeding the original strength of 375 MPa. The maximum recovered strength of ~422 MPa was achieved in the healed Ti₂AlC sample after healing at 1400 ℃ for 4 h, about 13% higher than the original strength. Damages were healed by the formed TiC_x from the decomposition of Ti₂AlC. The decomposition-induced crack healing as a new mechanism in the low oxygen partial pressure condition was disclosed for the MAX ceramics. The present study illustrates that key components made of Ti₂AlC can prolong their service life and keep their reliability during use at high temperatures in low oxygen partial pressures.