Constitutive modeling of TA15 alloy sheet coupling phase transformation in non-isothermal hot stamping process

The simultaneous occurrence of phase transformation and deformation for titanium alloy sheets is an important feature in hot stamping process where components are formed in room-temperature tools by hot blanks. This work takes a research on the constitutive modeling of TA15 alloy by coupling the effect of phase transformation under hot stamping conditions. Based on Gleeble testing system, the continuous cooling tests and interrupted tensile tests are conducted to study the effects of cooling rate and deformation on phase transformation. Subsequently, a diffusion controlled phase transformation model is extended to describe the phase transformation kinetics. The flow behaviors of TA15 alloy are found to be not only sensitive to temperature and strain rate, but also cooling rate dependent, which can be ascribed to the phase transformation. Hence, a physically based model coupling the effect of phase transformation is proposed. Compared with experimental stress–strain values, the average relative error of predicted results by the proposed model is 2.29%. Finally, hot stamping simulations and experiments of a U-shape part are performed. The simulation results of the proposed model show a better agreement with the experiments.