Demonstration of alloying, thermal activation, and latent hardening effects on quasi-static and dynamic polycrystal plasticity of Mg alloy, WE43-T5, plate

• Latent hardening is incorporated using estimates obtained from discrete dislocation dynamics simulations.
• This latent hardening permits accurate description of both the evolving flow stress and plastic strain anisotropy.
• Basal slip and extension twinning are found to be rate insensitive in the strain rate regime investigated.
• Strength modeling suggests precipitation has a similar effect on all the slip modes, which lowers the anisotropy.
• Solute atoms play a particularly strong role in strengthening the slip and extension twinning modes.

The mechanical response of rare earth containing Mg alloy, WE43, plates is found to be more isotropic, as compared to conventional alloys like AZ31, despite a moderately strong texture. In order to understand the grain-level deformation mechanisms which are responsible, the elastoplastic self-consistent (EPSC) polycrystal plasticity code, including the recently developed twinning–detwinning (TDT) model, is used to describe the homogeneous plastic flow of WE43-T5, plate at quasistatic and dynamic strain rates. Latent hardening of the slip modes is based on a recent discrete dislocation dynamics study in order to reduce the number of empirical fitting parameters without sacrificing model fidelity. The approach accounts for the presence of the initial texture and its evolution during deformation. The observed flow stress, strain, and strain hardening anisotropies and asymmetries are well-described. A single set of parameters was used to fit the entire set of results, at a given strain rate, thus enabling determination of strain rate sensitivities of individual deformation modes. Basal slip and extension twinning are rate-insensitive, within the strain rate regime examined, whereas the prismatic and slip exhibit strain rate sensitivities of 0.008 and 0.005, respectively. Various strengthening mechanisms such as precipitation, grain refinement and solid solution hardening effects on each individual deformation modes are assessed. The softer modes, basal slip and extension twinning, are greatly strengthened in this alloy, as compared to the harder modes such as prismatic and slip, which renders this material more isotropic, even at the grain-level, as compared to conventional Mg alloys.