Tensile deformation behavior of Ti-22Al-25Nb alloy at elevated temperatures

The deformation behavior of Ti-22Al-25Nb alloy at elevated temperatures and different stain rates was investigated using uniaxial tensile test. It was found that the tension was accompanied with the effect of hardening and softening, under which the stress-strain curve was characterized by a rise to a peak followed by a nearly linear drop in flow stress. The peak stress was strongly dependent on the temperature and strain rate. The underlying mechanism was clarified in terms of dislocation dynamics. Work hardening and strain rate hardening both contributed to the hardening mechanism, and the softening mode was dominated by dynamic recovery. The effect of work hardening was completely neutralized by dynamic recovery. Owing to the strain rate hardening, the alloy exhibited certain degree of superplasticity. The further drop in flow stress after the peak was due to the rise in temperature, which originated from the heat generated during deformation. The deformation mechanism was dominated by dislocation slip and climb. The misorientation distribution between beta/B2 and alpha 2 phase scarcely changed, implying a harmonious deformation of the two phases. (c) 2012 Elsevier B.V. All rights reserved.