Flow softening and dynamic recrystallization behavior of BT9 titanium alloy: A study using process map development

In the present study, uniaxial compression tests were employed between 1000 and 1100 °C under the strain rates of 10−3, 10−2 and 10−1 s−1 to investigate the hot deformation behavior of BT9 titanium alloy. Work hardening behavior interpretation and analytical investigations including calculation of deformation activation energy, and developing process maps were used to establish a numerical correlation between microstructural evolution and the flow behavior of the alloy. The results showed that dynamic recrystallization takes place at severe condition (T = 1000 °C and ε˙ = 0.1 s−1), while dynamic recovery is the major microstructural mechanism at other condition. According to dynamic material model and Prasad's instability criterion, the maximum power dissipation of 52% and 46% occur at 1000 °C/0.1s−1 and 1150 °C/0.001 s−1, respectively. Electron backscattered diffraction images and high resolution optical images also revealed that continuous dynamic recrystallization is the governing mechanism at these deformation conditions resulting in a significant grain refinement. Considering the calculated deformation activation energies, power efficiency domains and the microstructural observations, 1000 °C/0.1 s−1 was determined as the optimum deformation condition. •The correlation of the dynamic recrystallization and flow softening behavior.•Determination of the unsafe processing region using Prasad's instability criterion.•Contribution of continuous recrystallization as the main restoration mechanism.•The optimum condition for high temperature forming is proposed.