The prediction of hot deformation behavior in Fe–21Mn–2.5Si–1.5Al transformation-twinning induced plasticity steel

Prediction of the material flow behavior is an essential step to optimize designing any forming processes. This may be well addressed through applying a proper constitutive equation, which relates the stress and strain to the effective deformation conditions (i.e., temperature and strain rate). Accordingly in present study, the experimental true stress–true strain data from isothermal hot compression tests, in the temperature range of 800–1100 °C and strain rates of 0.001, 0.01 and 0.1 s−1, have been employed to develop the appropriate constitutive equations for a new grade of TRIP/TWIP steel. The effects of temperature and strain rate on the deformation behavior have been represented by Zener–Hollomon parameter in an exponent type equation. Employing an Arrhenius type constitutive equation, the influence of strain has been incorporated by considering the related material constants as functions of strain. The Q-values have been in the range of 390–424 kJ/mol for different amounts of strain. Finally, the accuracy of the developed constitutive equations has been evaluated using standard statistical parameters such as correlation coefficient and average absolute relative error. The results indicate that the proposed strain-dependent constitutive equation gives an accurate and precise estimate of the flow stress in the relevant temperature range.