Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy TIG-welded joint

Abstract Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas (TIG) welded joint were analyzed in detail. In weld zone (WZ), α+θ eutectic structure formed at grain boundaries with no precipitates inside the grains. In partially melted zone (PMZ), symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-like θ′ phases appeared in the secondary heated zone. In over aged zone (OAZ), the coarsening and dissolution of θ′ phases occurred and most θ′ phases transformed into θ phases. In general heat affected zone (HAZ), θ′ phases coarsened. Factors such as the strengthening phases, the grain size, the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint. Moreover, a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates, the average diameter of precipitates and the concentration of soluble elements was proposed.