Research on constitutive models and hot workability of as-homogenized Al-Zn-Mg-Cu alloy during isothermal compression

Hot compression tests of as-homogenized Al-Zn-Mg-Cu alloy were performed at the deformation temperature range of 350-450 A degrees C and the strain rate range of 0.001-1 s(-1). The Arrhenius-type constitutive equation and the Avrami-type model were established to predict the flow behaviors of the alloy respectively. The processing map at the true strain of 0.92 was developed to evaluate the workability of the alloy and the related microstructures were investigated. The results show that the Avrami-type model has a higher accuracy to predict flow stress than the Arrhenius-type constitutive equation. The stable deformation occurs under high temperature or low strain rate mainly owing to the dynamic recrystallization. Flow instability is prone to occur under the condition of low temperature and high strain rate due to the initiation and the propagation of micro-cracks. According to the processing map and corresponding microstructure characteristics, the optimum processing parameters are in the temperature range of 380-405 A degrees C and the strain rate range of 0.006-0.035 s(-1).