Microstructure and mechanical properties of AA6056 friction stir welded plate

Abstract

The microstructure and mechanical properties of a friction stir welded AA6056-T6 aluminum alloy plate were investigated by using polarized optical and transmission electron microscopy techniques. The microstructure revealed different grain morphologies in the thermomechanically affected zones, in proximity of the weld nugget; as the advancing side had fairly elongated, bent grains, whilst the broader retreating side had elongated grains whose width is narrower compared to the advancing side. On both sides, the thermo-mechanical affected zones showed a process of grain subdivision due to shear strain and temperature increase on approaching the nugget zone. Along with overaged precipitates in both thermomechanically affected zones, ß? and ß' particles were detected only within the retreating side. Tensile tests showed yield and ultimate strength slightly lower across the weld compared to the parent material; this difference resulted in a reduction in ductility of the weld region.