High temperature creep behaviour in the γ titanium aluminide Ti–45Al–2Mn–2Nb

The fact that Gamma titanium aluminides (γ-TiAl) offer strong potential for replacing conventional titanium and nickel-base alloys in future gas turbine engine designs has resulted in the requirement to accurately describe the creep behaviour of these complex alloys. Consequently, the system Ti–45Al–2Mn–2Nb has been extensively studied under high temperature creep conditions where creep ductilities are shown to far exceed the relatively low tensile ductilities characteristic of the alloy at room temperature. Modern lifing approaches have been applied to the alloy, helping to develop understanding of the deformation behaviour, and are shown to accurately describe the stress-rupture and minimum creep rate behaviour of the alloy, promoting confidence for the derivation of computational models which are used to describe the behaviour of the alloy for in service conditions. When compared to an existing, conventional, high temperature titanium alloy, Timetal 834, significant improvements in creep life were demonstrated for equivalent stress conditions with a comparable level of creep ductility between the two alloys. In addition, the gamma titanium aluminide showed a superior resistance to surface oxidation and associated cracking with notable α case formation in Timetal 834 leading to premature failure.

► The creep of Ti–45Al–2Mn–2Nb alloy was precisely described through the Wilshire equations.
► The Ti–45Al–2Mn–2Nb demonstrated significant improvements in temperature and stress capabilities.
► The Ti–45Al–2Mn–2Nb showed a superior resistance to surface oxidation and cracking.
► The ductility of Ti–45Al–2Mn–2Nb is very encouraging, consistently exceeding 15%.
► The Ti–45Al–2Mn–2Nb alloy showed improvements over the titanium alloy Ti834.