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This work investigated the effect of a slight increase in Nb content of approximately 1 at.% and the effect of adding a minor Sc or La-rich Misch metal (Mm) on the microstructure, phases and high temperature properties of Ti–40Al–15Nb alloy. Microstructural analysis and phase characterizations of the Ti–40Al–16Nb alloy with 0.39 wt.% Sc or La-rich Misch metal additions are summarized as follows. (i) The as-cast Ti–40Al–16Nb–0.39 wt.% M (M=Sc or Mm) alloys have an α₂ matrix and contain α-Ti and B2 phase precipitates but few γ phase precipitates. The Sc₂O₃ or La₂O₃ oxide dispersoids, formed by internal oxidation, are observed in this work; but Ti₃(Al,Sc) presented in the dual phases of γ-TiAl were not found. (ii) Adding Sc and La-rich Misch metal decreases the α-transus temperatures of the TiAl–Nb alloys, possibly stabilizing the α₂ phase and inhibiting the B2 or γ phase formation. (iii) After homogenization …