Abstract Since 2012, intermetallic alloys based on the γ(TiAl) + α2(Ti3Al) phases have been used as a material for low–pressure turbine blades in gas turbine aircraft engines replacing conventional nickel–based superalloys. However, the use of these alloys remains limited. This is due not only to their inherent brittleness and low crack resistance, but also to insufficient creep and oxidation resistance at temperatures of 700–750°C and above. In the present work, novel physicochemical approaches to alloying intermetallic alloys based on γ(TiAl) + α2(Ti3Al) phases were proposed, followed by their practical implementation. According to the proposed approaches: i) the alloying elements should have high solubility in intermetallic phases; ii) it is preferable for the alloying elements to be refractory metals and have larger atomic radii than Ti and Al; iii) it is desirable that the alloying reduces the lattice misfits of the γ(TiAl) and α2(Ti3Al) phases; iv) it is preferable that the alloying does not lead to an increase in the content of the brittle α2(Ti3Al) phase and an increase in the tetragonal distortion of the γ(TiAl) phase; v) the difference in electronegativity of the alloying elements and the base elements (Ti and Al) should not be too significant. To achieve the goal, the alloys based on Ti–(43.5–44)Al (at. %) and alloyed with elements meeting the specified conditions were manufactured and subjected to the same hot working and heat treatment, which ensured obtaining similar microstructural conditions. This made it possible to elucidate the effect of alloying on mechanical properties and oxidation resistance of the alloys. Based on this, a new TNZ alloy with the composition Ti–(43.5–44.5)Al–6(Nb, Zr, Hf)–(0.1–0.15)B (at. %) was designed. It was demonstrated that the new alloy possessed enhanced creep and oxidation resistance in comparison with that of the engineering TNM alloy (Ti–43.5A–4Nb–1Mo–0.1B, at. %) without compromising ductility and hot workability.
Imayev et al. (Mon,) studied this question.