Low cycle fatigue of thin copper foils

The fatigue and monotonic tensile properties of two electrodeposited and one wrought thin foil of copper were measured in a way similar to that used for bulk in order to determine if there is a difference. The graphs of the Basquin equation, which all foils obeyed, of the thin and the bulk wrought copper differed only slightly indicating that the thickness had only a minor effect on the fatigue properties. The order of the magnitudes of the fatigue strength coefficients was the same as that of the tensile strength being larger for the electrodeposited foils. The higher strength of the plated foils was attributed to higher dislocation and twin densities and smaller grains. The fatigue strength coefficients were related to the cyclic hardening exponents. Cyclic hardening, which occurred primarily in the initial stages of fatigue, was a result of dislocation tangle and cell-wall formation when the grain size exceeded 2 mu m. No dislocation cell structures were observed when the grain size was smaller than 2 mu m.