Establishment of a novel constitutive model considering dynamic recrystallization behavior of Ti-22Al-25Nb alloy during hot deformation

The hot deformation behavior of Ti-22Al-25Nb alloy fabricated by hot compressed sintering was investigated under various conditions of compression tests in the deformation temperature range of 975-1075 degrees C with 20 degrees C intervals and the strain rate range of 0.001-1.0 s(-1). Based on the experimental data, a novel constitutive relation combining a series of models was developed, including Zener-Hollomon parameter (Z), DRX critical model and kinetics model. The results show that the hot-deformed activation energy Q is calculated to be 410.172 kJ/mol, the ratio of critical strain (epsilon(c)) to peak strain (epsilon(p)) is a constant value of about 0.67. The predicted stress obtained by the established constitutive equations matches well with the true stress from experimental data. Despite large errors occur at the stage where strain rate is 0.1 s(-1) and the values of true strain are less than 0.1, the stage of large strain should be more concerned during plastic forming. Furthermore, the predicting accuracy with the DRX kinetics model was testified by an electron back-scattered diffraction (EBSD) technique.