Finite element implementation of a kinetic model of dynamic strain aging in aluminum-magnesium alloys

Soare and Curtin (Acta Mater. 2008; 56:4091-4101, 4046-4061) have recently developed a model of dynamic strain aging in solute-strengthened alloys. Their constitutive law describes time-dependent solute strengthening using rate equations that can be calibrated using atomistic simulations. In this paper, their material model is incorporated into a continuum finite element simulation, with a view to completing a multi-scale method for predicting the formability of solute-strengthened alloys. The Soare-Curtin model is first re-formulated as a state-variable constitutive law, which is suitable for finite element computations. An efficient numerical procedure is then developed to track the strength distribution of aging mobile and forest dislocations in the solid during deformation. The method is tested by simulating the behavior of a 3D aluminum-magnesium alloy tensile specimen subjected to uniaxial loading at constant nominal strain rate. The model predicts the influence of strain rate on the steady-state flow stress of Al-Mg alloys, but no Portevin-Le Chatelier bands or serrated flow were observed in any of our simulations, and the influence of strain rate on tensile ductility is not predicted correctly. The reasons for this behavior and possible resolutions are discussed. Copyright (C) 2010 John Wiley & Sons, Ltd