Fatigue Crack Initiation Behavior of Welded AA5083 in a Seawater Environment

Aluminum Alloy 5083 is increasingly used in the ship building industry due to its excellent corrosion resistance and its favorable mechanical properties. A significant application of this alloy is in high speed ferries, where the influence of dynamic loads is of great importance as well. However, the influence of a corrosive environment and/or a welded condition on the fatigue properties of nautical aluminum alloys has been studied only superficially. In the present paper the influence of a seawater environment in combination with a welded state is described. Both fatigue limits and SN-curves are given, as well as a fracture surface analysis. From these results the fracture and crack initiation mechanisms are explained. Particularly the penetration of seawater into sub-surface pores, that are present in the welded material, results in a significant drop in fatigue life time when the welded alloy is tested in seawater.