Welding Heat Input and Post-Weld Heat Treatment Effects on Joint Material Mixing and Weld Integrity of Friction Stir Welded Dissimilar Aerospace Alloys

This study investigated the effects of heat input on the mechanical behaviour and joint materials mixing pattern and post weld heat treatment (PWHT) on welded 6101-T6 and 7075-T651 aerospace alloys via friction stir welding technology. The results obtained shows that the heat input tremendously affects the materials mixing at the joints during the welding operations and the post weld heat treatment also significantly impact on the mechanical behaviour of the welds. The tensile result indicates that the lowest heat input gave the highest tensile strength of 145 Mpa and highest average hardness value of 144 HV at the nugget zone. The dissimilar materials at the joint interface were found to flow into each other considerably in all the welds. However, the lowest heat input gave a better material mixing. This indicate that lower heat input generally improves the mechanical properties and material mixing at the joint interface of the welds. The heat treatment performed on the welds improves the tensile strength tremendously but lowers the hardness values when compared to those in as weld conditions.