Fabrication of in-situ Ti(C,N) phase toughened Al2O3 based ceramics from natural bauxite

Abstract

Al2O3–Ti(C,N) ceramics were fabricated via carbothermal reduction nitridation method with high-titania special-grade bauxite as the raw material. The formation mechanism of in-situ Ti(C,N) phase and its effect on the properties of materials are discussed. After nitrided at 1700 °C, Ti(C,N) phase could be formed in-situ with appropriate C/TiO2 molar ratio. Due to the residual stress field formed by Ti(C,N) particles, the path of crack propagation is changed, leading to the crack deflection and pinning. Therefore, the mechanical properties of the materials are improved by forming in-situ Ti(C,N) phase. With a C/TiO2 molar ratio of 2.2 and nitridation temperature of 1700 °C, Al2O3–Ti(C,N) ceramic with a hardness of 13.9 GPa, a fracture toughness of 8.28 MPa m1/2 and a flexural strength of 387 MPa could be fabricated.