Bending Fatigue Damage Behavior of Annealed Polycrystalline Cu Foil

Abstract

The metal foils at micrometer scale are applied in micro-electromechanical systems (MEMS) and devices widely, which the mechanical behaviors of them are significantly different from that of bulk materials and thin films constrained by a substrate. In this paper the annealed polycrystalline Cu foil with two thickness (t =100, 150 μm) was applied on the cantilever beam bending fatigue testing as a model material. The fatigue properties and the damage behaviors of the annealed polycrystalline Cu foil at the total strain control was investigated. The results showed that the bending fatigue life of the polycrystalline Cu foil with the grain size (d =9.2 μm) was significantly larger than that of the Cu bulk and thin Cu films with t =3 μm under the same strain range. The fatigue damage formation of the extrusions/intrusions and cracks along grain boundaries on the Cu foil surface caused fatigue fracture and final failure.