The flow behavior and the deformation mechanisms of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy during isothermal compression

The effects of the processing parameters on the shapes of flow curves, the microstructural evolution and the strain rate sensitivity are analyzed via the isothermal compression tests of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy. The isothermal compression is performed on a Gleeble-1500 thermal simulator in the deformation temperature range of 1103-1243 K, strain rate range of 1.0 × 10^-2 to 5.0 s^-1 and strain range of 0.2-1.2. The softening mechanisms are investigated thoroughly in the α+β phase region and β phase region through the experiments of optical microscopy, scanning electron microscopy and transmission electron microscopy. Then, the correlation between the flow behavior and the microstructural evolution is discussed. The results show that more noticeable flow softening at a high strain rate (5.0 s^-1) in the α+β phase region arises from the thermal softening, the dynamic recovery and the dynamic recrystallization of alpha phase. However, the thermal softening can no longer be considered to be the major softening mechanism at a low strain rate (1.0 × 10^-2 s^-1). In the β phase region, the dynamic recovery and the dynamic recrystallization of β phase are main softening mechanisms. Moreover, the maximum m value of 0.3 occurs at a deformation temperature of 1163 K, a strain rate of 0.1 s^-1 and a strain of 0.7, in which the microstructure is equiaxed and uniform.