Crack-healing behavior and strength recovery of hot-pressed TZ3Y20A-MoSi2 ceramics

Crack-healing behavior and strength recovery of ZrO2(Y2O3)-Al2O3-MoSi2 (TZ3Y20A-MoSi2) ceramics have been investigated. Heat treatment in air enhances distinctly the flexural strength of TZ3Y20A-MoSi2 ceramics. Si-O oxide and ZrSiO4 are found after heat treatment, in which the former heals the cracks and recovers the strength, however, the latter is one kind of brittle materials that reduces mechanical performance of ceramics. The TZ3Y20A-10 vol% MoSi2 ceramic has a complete crack-healing effect and strength recovery by suitable heat treatment at 1373 K for 3 h in air, however, the strength does not recover completely under other heat treatment conditions. With further increasing the MoSi2 contents to 20 vol%, the flexural strength of as heat-treated TZ3Y20A-MoSi2 ceramics is higher than that of pre-cracked specimens, but remains lower than that of smooth specimens. Crack closure and rebonding of the crack walls are due to the formation of Si-O glassy phase by oxidation reaction.