Effect of texture on deformation behavior of heterogeneous Mg-13Gd alloy with strength–ductility synergy

Abstract

Heterostructure metals as a new class of materials can effectively break the traditional strength–ductility trade-off dilemma. In this study, the extruded sheet with the small extrusion ratio (ER) of 3.9 (ER3.9) presented a heterogeneous lamella structure (HLS) and texture, where the fine dynamical recrystallized (DRXed) grains formed a random texture and coarse un-DRXed grains exhibited a strong basal texture. The ER3.9 sample presented an excellent combination of strength and ductility. The texture strengthening in coarse grains and hetero-deformation induced (HDI) strengthening contributed to the enhanced strength of the ER3.9 sample besides grain refinement. The improving ductility mainly stems from the weakened texture in fine grains. Interestingly, in coarse grains, the strong basal texture, the occurrence of cross slip, low stacking fault energy (SFE), and dislocation pinned by precipitates weaken the HDI hardening effect. While the traditional dislocation hardening mainly generated by fine grains dominates overall strain hardening. Meanwhile, the activation of non-basal slips, especially pyramidal 〈c + a〉 slip, and the generation of cross slips in fine grains benefit for coordinating plastic deformation. The ability for coordinate plastic deformation in fine grains is higher than that of coarse grains, which was confirmed by the digital image correlation technology. This work will promote the development of the heterogeneous theory in textured Mg alloys.