Design of pure aluminum laminates with heterostructures for extraordinary strength-ductility synergy

Heterogeneous metals and alloys are a new class of materials with superior mechanical properties. In this paper, we engineered sandwich-structured pure aluminum laminates composed of middle coarse-grained layer and outer fine-grained layer via extrusion, rolling and annealing. By controlling the post-annealing regimes, a larger degree of microstructure heterogeneities such as boundary spacing, misorientation and texture across the hetero-interface were obtained, which resulted in obvious mechanical differences. Tensile tests indicated that the 300 degrees C/30 min annealed laminates enabled a relatively high tensile ductility while simultaneously retaining a high strength, which was better than prediction by the rule-of-mixture. To explain the reasons behind it, the evolution of geometrically necessary dislocations and strain gradient at the hetero-interface zone were detected using in-situ tension and microscopic digital image correlation technique. It was found that with the increasing applied strain, a significant strain gradient was developed near the interface, which was accommodated by geometrically necessary dislocations, thereby contributing to higher hetero-deformation induced (HDI) strengthening and hardening. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This paper presents the fabrication of sandwich-structured pure aluminum laminates and investigates the mechanical differences resulting from microstructure heterogeneities at the hetero-interface. The annealing process is controlled to obtain a larger degree of heterogeneities, which contribute to higher tensile ductility and strength. The study also reveals the significant strain gradient and the involvement of geometrically necessary dislocations, which contribute to the hetero-deformation induced strengthening and hardening.