Influence of cooling environment on microstructure and mechanical properties of AA6082-T6 and AA7050-T7 dissimilar friction stir welds

This work developed dissimilar friction stir welded joints of AA6082-T6 and AA7050-T7 under different cooling environments namely conventional air, forced air, and water-cooling. Characteristics of developed weld joints were studied for macrostructure, microstructure, microhardness, tensile properties, and fractography. AA6082-T6 dominated in weld nugget macrostructure and proportion of same increased with increasing cooling rate, while weld width reduced remarkably with an increase in heat extraction rate. Welds had interlocking lobes-based flow structures superimposed over an intercalated lamellar layer of both metals. The cooling environment significantly affected the proportion of low/high angle grain boundaries, tensile properties, and hardness of weld nugget zones. The tensile specimens of all-welded joints were fractured from minimum hardness location in a ductile mode.