Enhancement of mechanical properties and oxidation resistance of TiAl alloy with addition of Nb and Mo alloying elements

In this study, small button-shaped ingots were prepared by a non-self-consuming vacuum arc melting method. The effect of the content of Nb and Mo elements on the microstructure, mechanical properties and oxidation resistance of TiAl alloys were investigated. The as-cast TiAl alloy presented laminar microstructure. When only adding Nb element, a small amount of β phase was distributed in the form of dots at the grain boundaries of α₂/γ lamellar structure. When adding both Mo and Nb, the precipitated β phase started to precipitate in lines inside the α₂/γ lamellar structure. The microhardness of the alloy increased with the increasing Nb and Mo content. The compressive strength of the alloys increased firstly with the increasing Nb content and decreased when the content of Nb exceeded 7 wt%. However, with the addition of Mo, the compressive strength of the alloys decreased drastically. The optimal compressive strength of the alloy, i.e. 2250 MPa, was obtained with 5 wt% Nb and 5 wt% Mo addition. The oxidation resistance of the alloys were enhanced with the addition of Nb and Mo elements and the TiAl–5Nb–5Mo alloy also showed the best oxidation resistance at 800 °C.