Interfacial microstructural evolution and mechanical properties in dissimilar A1050 aluminium and S45C carbon steel friction stir welded joints using Zn interlayers

Abstract

This study investigated the effect of Zn interlayers on the dissimilar friction stir welding of A1050 pure aluminium and S45C carbon steel. Two joints were made by adding Zn foils of two different thicknesses (100 μm and 200 μm) between the A1050 and S45C base metals in addition to a third joint without any interlayer. The joining experiments were conducted in constant process parameters at tool rotational speed and welding speed of 1500 rpm and 250 mm/min, respectively. The differences in joints microstructure were correlated with their mechanical properties and fracture mode. The results showed that Zn inhibited the growth of the interfacial Al–Fe IMCs, altered their composition and contributed to strengthening the A1050 stir zones by forming Al–Zn solid solution. Compared to the Zn-free joint, the ultimate tensile strength of the joints fabricated with the 100 μm and 200 μm thick Zn interlayers was improved by 14% and 26%, respectively. Also, the brittleness inside their interfacial IMCs was eliminated. As a result, the joints fabricated with Zn interlayers exhibited higher elongation and their fracture occurred at the A1050 instead of the joint interface as in the Zn-free joint. The Zn interlayer is expected to widen the joining process window by minimizing the detrimental effects of the Al–Fe IMCs.