The influence of high temperature exposure on the mechanical performance of a γ titanium aluminide alloy

The influence of a prolonged high temperature air exposure on the tensile and fatigue behavior of a γ titanium aluminide (Ti–46Al–2Nb–2Cr–1Mo–0.2B, at.%) has been examined as a function of temperature, ambient to 760 °C. The embrittled surface layer has an effect on both properties. While the effect on tensile ductility diminishes as the interrogation temperature is increased, the influence on fatigue strength is most pronounced at the intermediate temperature of 540 °C. This appears to be linked to the minimum in fatigue crack growth resistance that is associated with this temperature regime. The effect of high temperature exposure has been effectively modeled, based on the initial crack sizes observed on the fracture surfaces, using an integration of the crack growth rate. However, the threshold observed in standard long crack specimens appears to be non-conservative.