Welding Metallurgy of

Temperature evolution, microstructure and mechanical properties of friction stir welded thick 2219-O aluminum alloy joints

Microstructure and mechanical properties of friction stir welded joints in 2219-T6 aluminum alloy

The study on defects in aluminum 2219-T6 thick butt friction stir welds with the application of multiple non-destructive testing methods

Microstructure and mechanical properties of laser beam-welded AA2060 Al-Li alloy

Aluminum Alloy 2219 was welded by gas metal arc welding and the microstructure was examined in the partially melted zone (PMZ), which is a narrow region immediately outside the fusion zone. Extensive liquation was observed at three different locations: at large {theta} (Al{sub 2}Cu) particles, along grain boundaries (GBs) and at numerous isolated points within grains. Liquation was initiated at the eutectic temperature T{sub E}, by the eutectic reaction {alpha} + {theta} {r_arrow} L{sub E} and intensified by further melting, above T{sub E}, of the {alpha} matrix surrounding the eutectic liquid (L{sub E}). The microstructure of the liquated-and-solidified GB material is intriguing. First, the material consisted of a new GB of mostly thin, divorced eutectic and a eutectic-free strip of {alpha} immediately next to it. Second, within an individual grain, the strip was along the top and the side facing the weld. Third, with respect to the weld, the strip was always behind the new GB. These three characteristics point to an important phenomenon, that is, solidification of the liquated GB is directional - upward and toward the weld, as a result of the temperature gradients across the PMZ. A thin, brittle eutectic GB and a soft ductile {alpha} stripmore » side by side are expected to be much weaker than a normal GB before welding.« less

C. Huang

Papers

Partially melted zone in aluminum welds -- Liquation mechanism and directional solidification