High-temperature oxidation behavior of multi-phase ceramic particles-reinforced TiAl composites with different microstructures

The high-temperature oxidation behaviors of multiphase ceramic particle-reinforced TiAl composites with different microstructures were investigated. The TiAl composites were prepared via spark plasma sintering by introducing 0.5 wt % graphene oxide and 0.3 wt% SiC into Ti-48Al-2Nb-2Cr. The near-γ equiaxed microstructure, dual-phase microstructure, and nearly fully lamellar microstructure were obtained by sintering at 1200, 1250, and 1300 °C, respectively. Moreover, multiphase ceramic particles were uniformly distributed in the TiAl matrix. Cyclic oxidation was conducted at 950 °C in air for 100 h. The TiAl composite with the nearly fully lamellar microstructure exhibited the best oxidation resistance (mass gain of 1.83 mg/cm²) and that with the near-γ microstructure exhibited the worst oxidation resistance (2.47 mg/cm²). The superior oxidation resistance of the TiAl composite with the nearly fully lamellar microstructure is attributed to the uniform distributions of Ti₂AlC particles at the α₂/γ lamellae interfaces and Ti₅Si₃ particles at the lamellae colony boundaries, which hinder atomic diffusion. Moreover, the α₂/γ lamellae colonies facilitate the formation of Nb-rich and Cr-rich phases at the interface of the oxide layer and substrate, which act as a protective barrier against atomic diffusion.