Effect of layer thickness on mechanical properties of Cu/CoCrFeNi nanolaminates: Implications from a quantitative flow stress model

Abstract

The excellent mechanical properties of metallic nanolaminates are closely related to the thickness of each individual layer (h). In this work, we comparatively investigated the effects of h on the mechanical properties of coherent Cu/CoCrFeNi and Cu/Ni nanolaminates under uniaxial compression using molecular dynamics simulations. It showed that with the decrease of h, the mechanical properties of the nanolaminates would be improved significantly. As h is decreased to a few nanometers, the flow stress of Cu/CoCrFeNi nanolaminates ascends to a plateau, while that of Cu/Ni nanolaminates descends. Two deformation mechanisms: dislocations slip constrained within layers and slip across interface, were revealed for the Cu/CoCrFeNi nanolaminates. Furthermore, the underlying mechanisms by which the Cu/CoCrFeNi and Cu/Ni nanolaminates exhibit different flow strength trends are revealed from the perspective of dislocation density. A model extended from the confined layer slip and interface barrier strength model was proposed to quantitatively estimate the flow stress of Cu/CoCrFeNi nanolaminates at different temperatures and strain rates. The results presented would be of great significance for the development and application of Cu/HEA nanolaminates.