Size effects on tensile and fatigue behaviour of polycrystalline metal foils at micrometer scale

Tensile and fatigue properties of as-rolled and annealed polycrystalline Cu foils with different thicknesses at micrometer scale are investigated. Uniaxial tensile testing shows that with decreasing foil thickness the uniform elongation decreases for both as-rolled and annealed foils, while the yield strength and ultimate tensile strength increase for as-rolled foils, but those decrease for the annealed foils. For both the as-rolled or annealed foils, bending fatigue resistance decreases with decreasing the foil thickness. Deformation and fatigue damage behavior of the free-standing foils were characterized as a function of foil thickness. In addition, the fatigue strength of various small-sized Cu foils was compared to understand the physical mechanisms of size effects on mechanical properties of the metallic material at micrometer scales.