Dynamic softening behavior of TC18 titanium alloy during hot deformation

Dynamic softening behavior of TC18 titanium alloy have been investigated in this paper based on isothermal compression experiment. Strain-rate sensitivity coefficient m and deformation activation energy Q_def under different deformation conditions have been calculated through Arrhenius constitutive model. The dependence of strain-rate sensitivity and activation energy on deformation parameters has been analyzed from the perspective of internal variables. A function of deformation temperature has been proposed to estimate the self-diffusion activation energy Q_self for dual-phase titanium alloys. The dependence of DRX/DRV on deformation parameters has been demonstrated by novel methods. From comparisons between self-diffusion and deformation activation energy, deformation undergoing DRX has been identified with low strain rates and elevated temperatures. Finally, microstructure observation has been taken carried out to verify the applicability of the new methods. Meanwhile, Poliak-Jonas criterion and power dissipation efficiency distribution has been employed to discuss the dependence of softening behavior on deformation condition.