Effect of the welding parameters and tool configuration on micro- and macro-mechanical properties of similar and dissimilar FSWed joints in AA5754 and AZ31 thin sheets

The effect of welding parameters and tool configuration on the surface appearance, mechanical and microstructural properties of similar and dissimilar FSWed joints in AA5754 and AZ31 thin sheets was widely investigated. Two different tool configurations, with and without the pin, were used. As far as the similar friction stir welded joints in AZ31 and in AA5754 alloys are concerned, it was shown that the “pinless” tool leads to the obtaining of higher values of the tensile strength and ductility as compared to the “pin” one. On the contrary, by considering the dissimilar friction stir welding between AZ31 and AA5754 thin sheets, the welding process becomes very critical as the “pinless” tool is used. Sound dissimilar joints were obtained using the “pin” tool configuration, even though the effect of the material position with respect to the welding tool is a very important factor to be considered. A marked improvement in the surface appearance and mechanical properties was obtained by placing aluminium alloy in the advancing side and magnesium alloy in the retreating one. An investigation has been also carried out in order to evaluate the microstructural properties of similar and dissimilar welded joints.

► Similar and dissimilar FSWed joints in AA5754 and AZ31 thin sheets were obtained.
► The highest UTS and UE in similar welds were obtained using the pinless tool.
► The highest UTS and UE in dissimilar welds were obtained using the pin tool.
► Material position with respect the tool is a fundamental factor in dissimilar welds.
► The distribution of Al and Mg alloys is depth-dependent in dissimilar welds.