Localized Mechanical Properties of Friction Stir Processed Sensitized 5456-H116 Al

Abstract

The microstructures of Al-Mg alloys with greater than 3wt.% Mg can sensitize leaving the material susceptible to intergranular corrosion (IGC); sensitized microstructures are identified by the amassing of phase precipitates at grain boundaries. Friction stir processing (FSP) has previously been shown to increase the corrosion resistance of sensitized Al-Mg alloys through break-up of the continuous network of phase particles [1]. In this study, multi-pass FSP is applied to a sensitized 5456-H116 aluminum plate and the resulting microstructure is linked to local mechanical properties (0.2% yield strength, ultimate tensile strength, and elongation) obtained using micro-tensile specimens extracted transversely across the FSP region. In the FSP region, the original sensitized microstructure becomes unsensitized; the unsensitized region is not limited to the friction stir zone but extends outward several mm into the base material. Though the sensitized microstructure is removed, the mechanical testing within the affected area shows the strength and elongation decrease and increase respectively from H116 temper to O temper levels. The previously sensitized microstructure is not observed to have negatively affected the mechanical properties