Oxidation resistance of powder metallurgy Ti–45Al–10Nb alloy at high temperature

TiAl alloy with high Nb content, nominally Ti–45Al–10Nb, was prepared by powder metallurgy, and the oxidation resistance at 850, 900, and 950°C was investigated. The high-temperature oxidation-resistance mechanism and oxidation dynamics were discussed following the oxide skin morphology and microstructural evolution analysis. The oxide skin structures were similar for 850 and 900°C, with TiO₂+Al₂O₃ mixture covering TiO₂ with dispersed Nb₂O₅. At 950°C, the oxide skin was divided into four sublayers, from the outside to the parent metal: loose TiO₂+Al₂O₃, dense Al₂O₃, dense TiO₂+Nb₂O₅, and TiO₂ matrix with dispersed Nb₂O₅. The Nb layer suppressed the outward diffusion of Ti atoms, hindering the growth of TiO₂, and simultaneously promote the formation of a continuous Al₂O₃ protective layer, providing the alloy with long-term high-temperature oxidation resistance.