Piecewise Modeling of Flow Stress of 7075-T6 Aluminum Alloy in Hot Deformation

The flow stress behavior of the 7075-T6 aluminum alloy was studied through single-pass compression experiment by using simulator within temperature range of 573-723 K and strain rate range of 0.01-10 s(-1). The stress-strain curves are presented as three stages including work hardening, dynamic recrystallization and relative steady state. The stress increases to a peak value firstly and then decrease nonlinearly to an initial steady state within some strain. Subsequently, the stress shows as linear change after initial steady state. In order to describe the change of flow stress in the range of peak stress to initial steady state, a now model has been developed based on phenomenological representation of the shape and the boundary conditions of the curves. Furthermore, a new material parameter C-2 and k which are sensitive to the temperature and strain rate were proposed in the developed constitutive model. The equations expressed in terms of peak stress and strain, steady state stress and strain and additional parameters. The stress-strain curves of 7075-T6 aluminum alloy obtained by this model are in good agreement with experimental results consequently that the method proposed is valid and the model is reliable.