A constitutive description for aluminum-0.1 pct magnesium alloy under hot working conditions

The constitutive behavior of an aluminum 0.1 wt pct Mg alloy deformed in the temperature range of 573 to 823 K at strain rates between 0.001 and 100 s⁻¹ is analyzed on the basis of the concept of the mechanical threshold stress (MTS), , taking into consideration the contributions from the different strengthening mechanisms that could be present in this alloy, , which include one component that arises from the interaction between dislocations and solute atoms, , and another contribution from the interaction between mobile and forest dislocations, . The evolution of is described in terms of a generalized form of an exponential-saturation equation, whereas the characterization of the ratio, s _i ( , T), between the flow stress at any strain rate and temperature, and the two components is carried out by means of the phenomenological model advanced by Kocks and co-workers. It is shown that the experimental values of the flow stress as well as the work-hardening rate can be accurately described following this approach and that the maximum difference between the experimental and calculated values of such a parameter is less than ±4 MPa. The analysis conducted from continuous stress-strain curves determined at constant temperature and strain rate indicates that the relaxation strain in the generalized form of the Sah et al. relationship displays a significant strain rate dependence. The inclusion of such a dependence into the analysis by means of a simple parametric relationship leads to an improvement in the accuracy of the prediction of the model.