Incorporation of Solid Solution Alloying Effects into Polycrystal Modeling of Mg Alloys

Discrepancies between the strength of slip systems determined directly from Mg single-crystal studies and those estimated from polycrystal simulations of Mg alloys are known to exist. These discrepancies have prohibited the direct use of single-crystal data within polycrystal models, ultimately leading to an increase in the number of adjustable parameters in such models and, accordingly, difficulties in extending such models to Mg alloys of industrial and technological relevance. In this work, a framework is introduced that eliminates these differences by accounting for continuum mechanical and physical metallurgical effects. With respect to the former, it is shown that a stiffer self-consistent grain–matrix interaction scheme than that commonly used better captures the behavior of textured Mg alloy AZ31. With respect to the latter, the impact of grain size and solute concentration on individual deformation modes is considered. Because of a lack of sufficient experimental data describing all possible deformation modes, only basal slip and prismatic slip are treated quantitatively. Of particular note is the strong solid solution strengthening of the basal slip mode and the moderate solute softening of the prismatic slip mode by the common alloying elements Al and Zn. An empirical model describing the Zn solute and temperature dependence of thermally activated prismatic slip is presented. The presented methodology provides a first attempt to eliminate the need for trial-and-error–based approach for determining the slip system flow stress parameters of polycrystal models. Areas where advances in the presented analysis may be attained are highlighted.