The crack‐healing behavior and oxidation resistance of Al₂O₃–ZrO₂–SiB₆ ceramic at 600–1200°C

In this paper, we prepared Al 2 O 3 –ZrO 2 –SiB 6 composite ceramics with excellent performance by introducing the second‐phase high‐strength healing agent SiB 6 in zirconia‐toughened alumina system, artificially created cracks using Vickers hardness tester, investigated the effects of heat treatment temperature (600–1200°C) and time (0–300 min) on the microscopic morphology and bending strength of the ceramics, revealed the healing mechanism, and studied the oxidation resistance properties. It was found that the healing effect was better at heat treatment of 90 min at 700°C and 60 min at 800°C, and the flexural strength was restored to more than 95% of that of the smooth specimens in both cases. Crack repair was mainly achieved by the reaction of SiB 6 , ZrB 2 , and B 4 C with O 2 . Below 800°C, healing was mainly achieved by the reaction of SiB 6 and B 4 C with O 2 , and the generated B 2 O 3 and SiO 2 migrated toward the crack to repair it. When the healing temperature is higher than 800°C, ZrB 2 also reacts with oxygen to produce B 2 O 3 and t‐ZrO 2 . It was found that the oxidation weight gain per unit area of the Al 2 O 3 –ZrO 2 –SiB 6 ceramic composite at different temperatures was small, and it has excellent oxidation resistance.