Microstructural Characterization and Mechanical Properties of Fusion Welded Dissimilar Joints of AA2219-AA5083 at RT, 77K and 20K

Abstract In the present study, 3 mm thick sheets of aluminium-copper alloy AA2219 were welded to aluminium-magnesium alloy AA5083 by tungsten inert gas (TIG) welding using AA2319 filler wire. The welded specimens were evaluated for mechanical properties at RT, 77 K, and 20 K. The failure of the tensile specimens was predominantly on the AA2219 side of the weld bead at all test temperatures down to 20 K. Microstructural analysis was carried out by optical and scanning electron microscopy. Based on extensive analysis of the weld joints tested at room and cryogenic temperatures down to 20 K, it was observed that the grain boundary copper rich films formed at the partially melted zone on the AA2219 side of the weld joint were weaker compared to the eutectics formed at fusion line/HAZ on the AA5083 side. This is further aided by the absence of phase mixtures of undesirable morphology in the weld region. This phenomenon is further corroborated with the dependence of the orientation of AA2219 grains with loading axis in repair welded AA2219–AA5083 weld specimens. When the tensile axis is perpendicular to AA2219 grains, failure was on the AA2219 side of the weld indicating that the strength of copper rich films in a partially welded zone decides the strength of weld joints. Finally, it is concluded that reliable dissimilar weld joints of AA2219–AA5083 of aerospace quality can be manufactured.