Metallurgical and corrosion features of friction stir welding of AA5083-H111

Friction stir welding is a solid state joining process, which has been considered the most important development in the welding technology, in the last decade, especially in the joining of light alloys such as aluminium alloys. The increasing applications of these materials in industry give rise to significant development of this process in world scale. The material analysed in this work is the non-heat treatable aluminium alloy AA5083-H111, strain hardened with significant applications, e.g., shipbuilding and automotive industries. Metallurgical features are investigated, such as, the diffusion of initial precipitates and changes of grain size in the heat-affected zone and thermal-mechanically affected zone, resulting from the thermal-mechanical cycle of the friction stir welding process. The results allow to understand the mechanisms that determine the metallurgical changes in the weld bead. The metallographic analysis is compared with hardness tests developed in all zones of the welded joint, enabling conclusions about the mechanical resistance efficiency. The localization and form of corrosion initiation is also evaluated, as well as the influence of the chemical composition of the solid solution matrix of aluminium and secondary phases in the susceptibility to corrosion of parent material and weld bead.