Mechanical properties of Cu/Ag multilayered composites

Cu–Ag multilayered nanocomposites, as well as pure copper samples, were made by electrodeposition using a single-bath cyanide solution. Two groups of composites with different bi-layer thickness values (about 330 and 110 nm, respectively) were produced. The thickness of the silver layers (≈10 nm) was the same in all samples. Annealing was conducted to investigate the stability of microstructure at low temperatures. The results of this study showed that the as-deposited laminated composites have a much higher strength relative to the electrodeposited pure copper. However, the effect of the copper layer thickness on strength was not significant. Annealing at 150°C caused the specimens in both groups to lose their strength to the level of pure copper specimens. Based on the microstructural and mechanical properties analyses, it is suggested that the high strength of the electrodeposited Cu/Ag laminated composites arises from the refinement of grains in the copper layers, the resistance of the silver layers to plastic deformation and the existence of coherency stresses at the layer interfaces. Annealing at 150°C results in a loss of strength owing to the recovery of microstructure, copper grain growth and consequent relaxation of interfacial stresses.