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γ-TiAl alloys,including two categories(the conventional TiAl and the high Nb-containing TiAl(high Nb-TiAl)),are technologically intriguing because of their applications at high temperatures.Specifically,the service temperature of the high Nb-TiAl alloys is 60-100℃higher than that of conventional TiAl alloys.Recently developed TiAl alloys,for example TNB,TNM,β-γ alloys,belong to the high Nb-TiAl alloys,displaying similar behavior in phase transformation,strengthening,oxidation at high temperatures,and relationships between composition,microstructure,and mechanical properties.This work presents an in-depth review of the high Nb-TiAl alloys regarding the advances in phase diagram,formation mechanism of the new γ_1 phase,microsegregation induced by adding a high content of alloying element Nb,and the mechanism of the B2/ω phase formation.Some challenges in developing the high Nb-TiAl alloys are also discussed.
γ-TiAl alloys, including two categories (the conventional TiAl and the high Nb-containing TiAl (high Nb-TiAl)), are technologically intriguing because of their applications at high temperatures. Specifically, the service temperature of the high Nb-TiAl alloys is 60-100 ℃ higher than that of conventional TiAl alloys. for example, TNB, TNM, β-γ alloys, belong to the high Nb-TiAl alloys, display similar behavior in phase transformation, strengthening, oxidation at high temperatures, and relationships between composition, microstructure, and mechanical properties. This work presents an in-depth review of the high Nb-TiAl alloys regarding the advances in phase diagram, formation mechanism of the new γ_1 phase, microsegregation induced by adding a high content of alloying element Nb, and the mechanism of the B2 / ω phase formation. Home challenges in developing the high Nb-TiAl alloys are also discussed.