Microstructural changes accompanying repair welding in 5xxx aluminium alloys and their effect on the mechanical properties

At the shipyards, the aluminium alloy 5083 is welded with a multi-pass sequence using the metal inert gas technique. If, while checking the weld integrity either after welding or during service, defects are detected in the vicinity of the weldment, repairs are usually employed to extend the service life. The repair method involves removal of the upper passes, depending on the thickness and re-welding under the same conditions. Purpose of this paper is to examine the microstructural changes accompanying repair welding, define their effect on properties of primary importance and set, if possible, an upper limit as far as the number of repairs is concerned.