Plastic Deformation Behaviors Of Cu/Ni Clad Foil In Uniaxial Micro-tension

Micro-system technology(MST)with small size,versatility,intelligence and high efficiency,which can be applied in many fields and prospects broad.The wide use of micro-system needs plenty of new materials to produce special micro-systems,such as Nano,alloy and multi-layer materials.The development of new materials is one of the future developments of micro-system technology,which greatly promotes micro-systems' development.According to the researching works of the existing mesoscopic new materials,lots of tests and studies had been made in the mechanical properties,forming technologies and parts of the metal monolayer material.However,the study of laminates has remained at the stage of preparation,for lack of research on it,which has limited their further application.The coupling free surface effect of the matrix layer and the non-negligible interface layer makes it difficult to predict the flow stress due to the decrease in the thickness of the specimen,it different with the single layer in mesoscopic scale and nor same as clad foil in macro scale.In this paper,the evolution of microstructures of copper/nickel clad foil and the thicknesses of interface and matrix layers is studied by changing temperature of the heat treatment with copper/nickel clad foils of 50?m and 100?m in thickness as experimental materials.After heat treatments,the grain sizes of copper layer and nickel layer increased as well as the thickness of the interface layer.On the contrary,the substrate thickness reduced.In order to investigate the plastic deformation behavior of copper/nickel clad foil,the clad foil after the heat treatment was uniaxial stretched.The results showed that the flow stress decreased with the increase of the grain size s.The flow stress of copper/nickel clad foil of 50?m in thickness was higher than that of 100?m in thickness at the same heat treatment temperature.As the heat treatment temperature increased,the work hardening of the copper/nickel clad foil decreased and the stress interval at each stage of the work hardening decreased.Based on the mixing rule and the surface layer model,con sidering the thickness,grain size and interface layer thickness of the cladding foil,the material constit utive was established.For exploring the fracture behavior of the cladding foil,the mechanical properties of the material such as yield strength,tensile strength and elongation were observed and analyzed.The appearance fracture showed that the grains were slipped on single in the matrix layer;and it had been found that it is a dimple fracture in the interface layer.According to the breaking experiment,it was found that the copper/nickel clad foil first cracked in the pores at the interface layer.With the increase of the strain,the cracks extended to the nickel layer,the nickel layer broke and the copper layer broke last.