The quasi-static and dynamic response of fine-grained Mg alloy AMX602: An experimental and computational study

A high strength magnesium alloy, AMX602 (Mg-6%Al-0.5%Mn-2%Ca), was manufactured by the spinning water atomization process (SWAP) and extruded into bar and plate geometries. Microstructural analysis using electron backscatter diffraction revealed that the processing produces an alloy with grains between 0.5 and 5 µm, with comparatively weak texture for Mg. The plate and bar had different textures–the former had a conventional hexagonal-close-packed (HCP) rolling texture and the latter a HCP extrusion texture. Quasi-static and dynamic compression experiments were performed to probe the material's mechanical behavior in the three processing directions. The experiments on each geometry revealed different anisotropic properties induced by a change in the active deformation mechanisms. The anisotropy was more pronounced at dynamic strain rates than quasi-static. A reduced-order crystal plasticity model that demarcates twinning, basal slip, and non-basal slip mechanisms was fit to the experimental data from the plate and bar. The model was consistent with experimental data and revealed that in the plate twinning dominated yielding in the extrusion and transverse directions, but slip dominated the normal direction. Yielding in the bar was dominated by twinning in the extrusion direction, but both slip and twinning were significant in the other two directions. The model showed the different anisotropic responses were due to the different textures produced during the processing of each geometry. Lastly, our data provided the basis for considering twinning to be rate insensitive in the model, which we confirm to be valid to at least 5000 s⁻¹.