Mechanical properties and deformation behavior of Mg-Al-Zn alloy laminate with multi-scale heterostructures

Abstract

Heterostructured materials as a new class can effectively avoid the inverted relationship of the “banana” curve followed by strength-ductility. The difference in grain size is the mainstream idea of the design of heterogeneous zones. However, the synergistic strengthening mechanism and deformation behavior among multi-scale heterostructures are still unclear. In this work, AZ80/AZ31 laminate with a multi-scale heterogeneous distribution of grain size, precipitates, and texture between alternate AZ31 and AZ80 component layers, which was constructed by accumulative extrusion bonding combined with aging treatment. The composite samples after 2-pass extrusion presented an outstanding strength-ductility synergy, which was attributed to the joint action of texture softening and hardening, grain refinement as well as multistage heterogeneous deformation induced (HDI) strengthening and hardening. Multi-types of heterogeneous regions provided more sites for geometrically necessary dislocation accumulation to accommodate multiple strain gradients under the constraint of multi-layer interfaces, enhancing HDI stress. The synergistic effect of great Schmid factor difference and increasing geometric compatibility factor between adjacent grains at the layer interface led to strain transfer behavior, which facilitated strain delocalization. This work expands the design ideas and preparation methods of heterostructured materials and enriches the theory of heterogeneous deformation.