Microstructure and mechanical properties of gas pressure sintered Al2O3/TiCN composite

Al2O3–30 wt.%TiCN composites have been fabricated successfully by a two-stage gas pressure sintering schedule. The gas pressure sintered Al2O3–30 wt.%TiCN composite achieved a relative density of 99.5%, a bending strength of 772 MPa, a hardness of 19.6 GPa, and a fracture toughness of 5.82 MPa m1/2. The fabrication procedure involves solid state sintering of two phases without solubility to prepare Al2O3–TiCN composite. Little grain growth occurred for TiCN during sintering while Al2O3 grains grew about three times to an average size of 3–5 μm. The interface microstress arising during cooling from the processing temperature because of the thermal and/or mechanical properties mismatch between the Al2O3 and TiCN phase is about 50 MPa. Such a compressive microstress is not high enough to cause grain boundary cracking that may weaken the composite but it can introduce dislocations within grains, which is very good to enhance the composite properties.