A thermo-viscoplastic constitutive model to predict elevated-temperature flow behaviour in a titanium-modified austenitic stainless steel

The experimental stress–strain data from isothermal hot compression tests over a wide range of temperatures (1073–1473 K), strains (0.1–0.5) and strain rates (0.001–1 s−1) were employed to formulate a suitable constitutive model to predict the elevated-temperature deformation behaviour in a Ti-modified austenitic stainless steel (alloy D9). It was observed that the Johnson–Cook (JC) model in its original form is inadequate to provide good description of flow behaviour of alloy D9 in the above hot working domain. This has been attributed to the inadequacy of the JC model to incorporate the coupled effects of strain and temperature and of strain rate and temperature. A modified constitutive model based on the Zerilli–Armstrong model has been proposed for considering the effects of thermal softening, strain rate hardening and isotropic hardening as well as the coupled effects of temperature and strain and of strain rate and temperature on flow stress. The proposed modified constitutive model could predict the elevated-temperature flow behaviour of alloy D9 over the specified hot working domain of alloy D9 with good correlation and generalization.