Effects of mechanical heterogeneity and dislocation storage capacity on the strength-ductility synergy of heterostructured laminates

Heterostructured laminates have attracted significant attention in the materials community owing to their exceptional combination of strength and ductility. However, long-standing questions remain regarding the impact of the strength difference between the soft and hard layers on the synergistic strengthening in heterolaminates with weak mechanical heterogeneity; the role played by soft/hard layers with various dislocation storage capacities on the strength-ductility synergy is also poorly understood. In this study, a series of typical heterostructured copper-brass laminates were fabricated using the diffusion welding + forging + rolling + annealing technique. The results demonstrated that larger microstructural and mechanical heterogeneities improved the strength-ductility combination of the hetero-laminates. The relatively weak mechanical heterogeneity and superior dislocation storage capacity of the soft copper and hard brass layers facilitated inter-layer synergistic deformation. This induced a gradual distribution of local strains and geometrically necessary dislocations (GNDs) near the hetero-interface. Thus, when evaluating the role of soft layers in synergistic strengthening, it is crucial to consider their generation and storage capabilities for dislocations.