Creep behaviour of Ti3Al-based titanium aluminide alloys containing molybdenum

Titanium aluminide alloys based on the intermetallic α2 phase, Ti3Al, are potential replacement materials for conventional titanium and nickel alloys in future gas turbine engines. This paper describes work carried out on the creep behaviour of two Ti3Al alloys, Ti-23Al-9Nb-2Mo-0.9Si and Ti-23Al-9Nb-2Mo-2V-0.9Si, tested in the temperature range 650–750 °C. Results are compared with the conventional titanium alloy IMI834. 3Al-based alloys have greatly enhanced creep strength, the equivalent of up to 90 °C increase in temperature capability. Creep strain accumulation has been modelled using the Graham-Walles equation, and predictions show a good fit to the experimental data over the full range of temperatures and stresses. For given creep life, the Ti3Al-based alloys have a relatively high primary creep strain, which must be considered during component design if the alloys are to be used to their full potential.