Fracture Analysis of Rodlike Mullite Particles in Mullite Matrix Ceramics

Mullite/mullite (rodlike) and ZTM/mullite (rodlike) ceramics with the microstructure of whisker toughening ceramics were fabricated. The research and analysis demonstrated that rodlike mullite particles had relatively high fracture strength; The growth of rodlike particles changed the fracture mode from the mainly transgranular to the mixture type of transgranular and inter granular in monophase mullite ceramics. A lot of rodlike particles pull-out from the matrix were observed in the fracture surface of the specimens. For ZTM, compressive stresses in the matrix would be produced by the phase transformation of ZrO2. So the bonding forces among the rodlike particles and matrix were enhanced and the debonding of rodlike particles became difficult. The pull-out of rodlike particles from matrix became less in the fracture surfaces and this phenomenon was even more obvious for the specimen with high m-ZrO2 content.