The identification of dynamic recrystallization and constitutive modeling during hot deformation of Ti55511 titanium alloy

Highlights: • Internal-variable identification method for the occurrence of dynamic recrystallization has been proposed. • Dynamic recrystallization occurs during hot deformation of Ti55511 alloy at low strain rates and moderate temperatures. • The strain rate sensitivity coefficient for dynamic recrystallization criticality is approximately constant at 1/6. - Abstract: In the present paper, an internal-variable identification approach has been proposed to investigate the dynamic recrystallization (DRX) behavior during hot deformation and corresponding constitutive model has been constructed. Isothermal compression experiments of Ti55511 titanium alloy were conducted for verification. Plastic behavior is determined by dislocation evolution in many cases while deforming. The comparison between saturated and DRX critical dislocation density was made to distinguish the occurrence of dynamic recrystallization/recovery (DRV) during hot deformation. The influence of deformation parameters on DRX behavior was illustrated by dislocation evolution map, validated by the power dissipation efficiency distribution. DRX process during hot deformation of Ti55511 alloy tends to occur under moderate temperatures and low strain rates. In addition, a physical-based Arrhenius constitutive formula has been derived for DRX criticality. The strain-rate sensitivity coefficients during hot deformation were fixed as a constant equal to 1/6 and the deformation activation energy was related to the material's self-diffusion activation.