A comparative study on the capability of Johnson-Cook and Arrhenius-type constitutive equations to describe the flow behavior of Mg-6Al-1Zn alloy

In the current study, the predictability of two phenomenological constitutive equations, Johnson-Cook (JC) and Arrhenius-type ones, for describing the flow behavior of a magnesium alloy (Mg-6Al-1Zn) under hot deformation conditions has been evaluated. Towards this end, a series of hot compression tests were performed over a temperature range of 250-450 °C, under strain rates of 0.001, 0.01 and 0.1 s−1. Using the experimental results obtained through implementing the predetermined compression tests, the related parameters and material constants in the constitutive equations were calculated. In order to compare the performance of the models, the statistical parameters of correlation coefficient and absolute mean error were employed. The results imply that the predictability of the Arrhenius-type equations is much stronger in estimating the flow behavior compared to that of the JC model; although more constants are needed to be calculated when using the former equation. It is concluded that the JC model, in contrast to the Arrhenius-type equations, is not reliable for the materials possessing tangible softening stage in their stress-strain curves such as magnesium AZ series.