State parameter-based constitutive modelling of stress strain curves in Al-Mg solid solutions

A novel and comprehensive approach addressing the stress strain response of binary Al-Mg alloys under uniaxial loading over a wide range of temperatures (78 K-650 K), strain rates (10−4-10 s−1) and solute contents (0 wt.%-5 wt.%) is developed and introduced. The model is based on the mechanical threshold Ansatz in combination with a Labusch type solid solution hardening approach and a model for dynamic strain ageing to describe the temperature and strain rate dependence of the yield stress in a thermal activation framework. Strain hardening is modelled on basis of the Kocks-Mecking evolution equations for the average dislocation density and discussed in terms of the temperature-dependence of the initial strain hardening rate and the saturation stress for stage-III hardening. Both, static and dynamic recovery, are fully taken into account. The model predictions are validated on experimental stress-strain curves reported in literature. The results demonstrate that the model successfully reproduces the complex temperature and strain rate dependent plastic deformation characteristics of Al-Mg alloys with a minimum of calibration input parameters.