Structure and formation mechanism of oxide scales of TiAl/TiB₂ composites at high temperature

The structure and formation mechanism of oxide scale of TiAl/TiB₂ composites at 1000°C in static air were investigated by XRD, SEM, EDS and TEM. The results show that the oxide scale of TiAl/TiB₂ composites includes an outer layer mainly consisting of TiO₂ grains and an inner porous layer which is the mixture of TiO₂ and Al₂O₃ grains. And TiO₂ outer layer is composed of an outer compact layer and an inner layer with pores similar to the shape of TiB₂. As the B₂O₃ which resulted from oxidized TiB₂ evaporates at the oxidation temperature, TiB₂ in the alloys increases the ratio of pores in oxide scale, and some of the pores in oxide scale come from oxidation of TiB₂. The oxidation resistance of TiAl/TiB₂ composites drops speedily when oxidation temperature is higher than 1000°C.