Twin-induced hardening in extruded Mg alloy AM30

The mechanical anisotropy of extruded Mg alloy AM30 was recently investigated, both experimentally and numerically (Oppedal et al., 2013 [1]). The authors highlighted the need to include cases of intermediate levels of twinning as a critical validation, in addition to the limiting cases where the contribution of twinning is dominant or negligible. However, further scrutiny of the results revealed that the experimental data employed in that study were still inadequate to constrain all necessary parameters in the crystal plasticity models. In particular, the parameters describing the prismatic slip mechanism were under-constrained. In the present study, additional experimental data were obtained to provide the necessary constraint. Based upon these experimental results, clearer conclusions can be drawn about the requirements of a crystal plasticity model, which must accurately account for strong tension-compression asymmetry as well as anisotropy in both strength and strain hardening behavior. In addition to the previously employed Viscoplastic Self-Consistent (VPSC) model, with the Predominant Twin Reorientation (PTR) scheme, the Elastic Visco-Plastic Self-Consistent (EVPSC) model, with the recently developed Twinning and De-Twinning (TDT) description, is applied to simulate the uniaxial response along arbitrary directions. It is demonstrated that accounting for the initial texture and calibrating the EVPSC-TDT model using uniaxial tension and compression along the extrusion direction permits prediction of the strength anisotropy and strain hardening behavior along arbitrary straining directions.