Interactive effects of microstructure and interface on tensile deformation behaviors of Cu/Ni clad foils

Abstract The plastic deformation behaviors are difficult to predict using the traditional theories because of the size effects induced by the interaction of intrinsic and extrinsic characteristics when the specimen sizes are scaled down to the micro/meso scale. In this study, uniaxial tensile tests of Cu/Ni clad foils under different heat treatments were carried out to investigate the coupling effects of microstructures and interface on the plastic deformation behaviors in the micro/meso scale. The traditional mixture rules, whether consider the interface layer or not, fail to analyze the strengths of Cu/Ni clad foils. The phenomenon was predicted via a proposed constitutive model which considers the interactive effect between the matrix microstructures and interface thickness of Cu/Ni clad foils, and the free surface effect in the micro/meso scale. A good agreement was seen between the calculated and experimental results. The experimental results also indicated that the ductility changed insignificantly with the annealing temperature and was enhanced compared to that of single-layer metal sheets. It was indicated by the experimental results of interrupt tests that the micro cracks originated from the interface and that the nickel layer and copper layer fractured successively due to their differences in mechanical properties and original micro voids at the interface between the Ni and Cu layers. The fracture mechanism was revealed by a proposed fracture model.