Strain-dependent constitutive modelling of AZ80 magnesium alloy containing 0.5 wt% rare earth elements and evaluation of its validation using finite element method

Abstract

In order to evaluate the hot flow behaviour of AZ80 magnesium alloy containing 0.5 wt% rare earth elements, isothermal hot compression tests were conducted at the temperatures range of 250–450 °C under the strain rates of 0.001–1 s−1. The flow curves exhibited a peak stress at a small applied strain after which the flow stresses decrease gradually to a steady state flow stress at higher applied strain values representing the occurrence of dynamic recrystallization. Moreover, the material constants in the Zener-Hollomon constitutive equation were found to be strain dependent, and the relationships between these parameters and the applied true strain were well described by fourth-degree polynomial functions. Accordingly, a strain-dependent model was developed in order to predict the hot flow behaviour of AZ80+0.5RE magnesium alloy. The true stresses predicted by this model were found to be in good agreements with the experimental results. Furthermore, the constitutive model developed using the experimental results was incorporated in the finite element model with which the hot compressive flow curve of the investigated material was modeled. The results showed that the accuracy of flow curves calculated by the numerical simulations depends on the accuracy of the developed model.