Abstract: AlN ceramics have high hardness and brittleness, and it is difficult to be sintered and dense. As a smelting vessel, it is damaged by high-temperature deformation or thermal shock caused by temperature change. AlN/YAlO₃ composite ceramics were prepared by pressureless sintering method by adding YAlO₃ as a particle reinforcement phase, and the thermal shock resistance of AlN/YAlO₃ composite ceramics at different temperatures was investigated. The phase structure, fracture morphology, and surface morphology of AlN/YAlO₃ composite ceramics before and after thermal shock were analyzed, and the mechanism of thermal shock damage was elucidated. The results show that the addition of YAlO₃ can promote the sintering and increase the density to 98.37% of AlN ceramics. The flexural strength and thermal shock resistance of AlN/YAlO₃ composite ceramics are improved due to the grain refinement. Especially in thermal shock experiments at higher temperatures, when the thermal shock temperature rises to 600 ℃, the flexural strength and residual strength ratio of AlN/YAlO₃ composite ceramics are significantly higher than those of AlN ceramics, indicating that the addition of YAlO₃ can effectively improve the thermal shock resistance of AlN ceramics. It is mainly attributable to microcrack toughening, crack deection and branching behavior slow down the reduction of flexural strength of AlN/YAlO₃ composite ceramics. Moreover, when the thermal shock temperature reaches 1 000 ℃, Al₂O₃ oxidated by AlN reduces severely the flexural strength of AlN/YAlO₃ composite ceramics.

Key words: AlN/YAlO₃ composite ceramics, thermal shock resistance, flexural strength, residual strength ratio, surface morphology, fracture morphology