Prediction of constitutive behavior and microstructure evolution in hot deformation of TA15 titanium alloy

• Physically-based microstructure models are established for constituent phases of the TA15 titanium alloy.
• The loss of Hall–Petch strengthening is modeled to predict the flow softening.
• Integrated constitutive models are developed for subtransus hot working of the titanium alloy.

A set of constitutive equations coupling microstructure evolution have been developed for hot working of a TA15 titanium alloy. Physically-based microstructure models were established for constituent phases of the material, which considered dislocation density variation, static coarsening, dynamic coarsening and strain induced grain refinement. The loss of Hall–Petch strengthening was modeled with aim to predict the flow softening. For each constituent phase, the microstructure model was implemented into a constitutive model for integrated prediction of flow stress and microstructure evolution. A visco-plastic self-consistent scheme was adopted to characterize the deformation heterogeneity from phase to phase and to predict the overall behavior of the aggregate. Model predictions, including flow stress, volume fraction and grain size of each phase, are in good agreement with experimental observations.