Microstructural evolution of aluminium in dissimilar A1050/S45C FSW joints by Zn interlayer

Abstract

This study investigated the microstructural evolution of A1050 stir zones in dissimilar A1050/S45C friction stir-welded joints fabricated with 100- and 200-µm-thick Zn interlayers in addition to a third joint without any interlayer. The dissolved Zn in the A1050 stir zones contributed to its strengthening by forming Al–Zn solid solution. The addition of Zn refined the A1050 grains with many well-defined high-angle grain boundaries. The effect of Zn in the A1050 strengthening and grain refinement becomes apparent with a relatively high content of Zn. The possible precipitation of Zn-rich particles along the A1050 grain boundaries may also contribute to the A1050 stir zone strengthening by retarding the dislocation motion and enhancing the discontinuous dynamic recrystallisation.