A Physical‐Based Constitutive Modeling Coupled With Dynamic Spheroidization and Phase Transformation for Bimodal Ti–6Al–4V Alloy Within α+β Region

The thermomechanical response and microstructure evolution of a bimodal Ti–6Al–4V alloy are investigated by isothermal compression tests within α+β phase region. Intensified flow softening, primarily driven by adiabatic heating and microstructure evolution, is observed at lower temperatures or higher strain rates. Microstructural analysis demonstrates that elevated temperature, strain, and strain rate collectively accelerate the α→β phase transformation, while large deformation coupled with higher temperatures or lower strain rates facilitates the spheroidization of lamellar α phase (α _L ). A physical‐based constitutive model is developed, incorporating four key mechanisms: (1) dislocation changes in each phase through work hardening, dynamic recovery, spheroidization of α _L phase, and dynamic recrystallization; (2) the reduction of Hall–Petch strengthening; (3) adiabatic heating effects; and (4) variations in β phase content. This model can successfully predict flow stress for bimodal Ti–6Al–4V within α+β phase region, confirming its effectiveness in optimizing deformation and forming parameters for this alloy.