In situ observation of destabilization of a nanostructured Ag/Cu multilayer fabricated via multicomponent accumulative roll bonding

Nanostructured metallic multilayered composites have many excellent properties due to their high-density heterophase interfaces, but they also pose challenges to the thermal stability of their multilayered structures. In this work, destabilization behavior of nanostructured Ag/Cu multilayer with an individual layer thickness of 40 nm prepared by multicomponent accumulative roll bonding is directly observed by transmission electron microscope. The results show that the destabilization of the nanostructured Ag/Cu multilayer originates from the interfacial instability perturbation driven by compositional gradient and capillary force. The subsequent destabilizing process is closely related to the cross-sectional ratio of the lamellar structure. When the thickness difference between adjacent lamellae is large, the lamellae with smaller thickness will follow a destabilizing sequence of perturbation → necking → pinching → termination migration. While the thickness of adjacent lamellae is similar, the perturbed lamellae tend to form stable grooves during roughening.