抄録
Fracture strength and fracture toughness tests were carried out on HIP-sintered TiB2 specimens at elevated temperatures and the mechanisms of strengthening and toughening by oxidation at elevated temperatures were investigated. Both the fracture strength and fracture toughness of TiB2 increased with increasing temperature up to 800-1100K and then decreased. The room-temperature strength of the specimens heated at elevated temperatures showed a similar temperature dependence of high-temperature strength. The mechanism of strengthening of the oxidized TiB2 seems to be as follows. When the TiB2 specimen is heated, the volumetric expansion due to the oxidation reaction of TiC→TiO2, where TiC is used as a sintering additive, occurs. This volumetric expansion near the surface oxidized region creates the residual compressive stress, which increases the strength and the fracture toughness.
