Understanding the deformation behaviours of Mg alloys with dispersed non-basal grain-embedded orientation heterostructures

Magnesium (Mg) alloys exhibit inferior ductility, caused by the very sharp texture originating from limited easily-activated slip modes. Although some strategies have been utilized to obtain weak-textured microstructures in Mg polycrystals, undesired decrease of strength usually occurs in accompany with improved ductility. Here, we fabricated dilute Mg-1Zn-1Sn-0.2Ca (wt.%, ZTX110) alloys with distinct orientation heterostructures, i.e., non-basal grains uniformly dispersed within the conventional basal texture, through elaborately-designed rolling/annealing processing. The orientation heterostructures exhibit superior ductility, ∼1.5 times as high as that of the basal-texture counterpart. A set of complementary characterization techniques have been utilized to reveal the deformation behaviors of orientation heterostructures over multiple-length scales. The strong intergranular interactions between basal and non-basal grains contributed to modifying the deformation behavior of the former via triggering non-basal slips. Moreover, the orientation heterostructure is beneficial to prevent the formation and propagation of macro-cracks, therefore delaying plastic instability and enhancing ductility. While the strength modification of orientation heterostructures depends on the volume fraction of non-basal grains. An orientation heterostructure with ∼32 % non-basal grains exhibits no apparent decrease in the strength, achieving superior strength-ductility combination. The hetero-deformation induced (HDI) strengthening offsets the strength loss of Mg alloys induced by texture weakening. These findings provide an innovative and feasible strategy of introducing dispersed non-basal grains to improve the mechanical properties of Mg alloys and can be extended to other hexagonal close-packed alloys.