Mechanical properties and deformation mechanism in Mg-Gd alloy laminate with dual-heterostructure grain size and texture

Abstract

Heterostructures can effectively break the traditional strength-ductility trade-off dilemma. However, how the texture of materials with heterostructure under hetero-deformation induced stress (including back stress and forward stress) influences the activation of the deformation mechanism is still not clear. In this paper, a Mg-1Gd/Mg-13Gd (wt.%) laminate with an alternating distribution of dual-heterostructure grain size and texture, where the coarse-grained (CG) layers presented a bimodal texture along the extrusion direction and the fine-grained (FG) layers showed random texture, exhibited an excellent strength-ductility synergy. Strain delocalization in the Mg-13Gd layer was realized by generating dispersed stable strain bands, which promoted the activation of ductile mechanisms. In the CG layers, the bimodal texture facilitated the activation of pyramidal <c + a> slip to maintain the continuity of strain at the interface. The lower level of geometric compatibility factor at the interface, with its heterogeneous texture, aggravated deformation incompatibility and boosted the back stress. The higher shear stress field at the interface generated by back stress led to the activation of pyramidal <c + a> slip and enhanced the strength of the CG layers. In the FG layers, the forward stress promoted the activation of prismatic <a> and pyramidal <c + a> slips at the interface; they acted together with the abundant basal <a> slips caused by the random texture to improve the ductility of the FG layers. The results of this work will promote the development of heterogeneous theory in textured Mg alloys.