Microstructure and mechanical properties of TiB2-Al2O3 composites

Effects of Al 2 O 3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing TiB 2 -30%Al 2 O 3 can be attained due to the plate-like TiB 2 particle and its random orientation and excessive Al 2 O 3 grain growth. When sintering temperature is higher than 1 700 °C, TiB 2 grain growth can be found, which obvious improves flexural strength of TiB 2 matrix but decreases toughness. It seems that mechanical properties of TiB 2 -Al 2 O 3 composites are mainly depended on relative density besides grain growth. otherwise, they will be determined by relative density and TiB 2 matrix strength together. Anyway, Al 2 O 3 addition can weaken the grain boundary and thus improve the toughness of the materials. A flexural strength of 529 MPa, Vickers hardness of 24.8 GPa and indentation toughness of 4.56 MPa·m 1/2 can be achieved inTiB 2 -30vol% Al 2 O 3 .