Explanation of high creep exponents in a gamma-based titanium aluminide intermetallic

The results of a recent study of creep deformation in an extruded Ti-48Al-1.5Cr alloy are presented in this paper. Secondary creep data are reported for the temperature regime between 700 and 900°C. Two-stage secondary creep deformation is shown to occur in this alloy over the temperature range that was examined. However, the secondary creep exponents were relatively high (approx. 8-14) in both regimes. The high creep exponents will be shown to be due to the effects of dynamic recrystallization phenomena in the nearly lamellar microstructure. The two-stage secondary creep behavior will also be attributed to a transition from diffusion-controlled creep at low stresses, to dislocation-controlled creep at high stress levels.