Modified friction stir clinching of AA6061-T6/AA5754-O joint: Effect of tool rotational speed and solution heat treatment on mechanical, microstructure, and fracture behaviors

The improvement of the modified friction stir clinched AA6061-T6/AA5754-O aluminum joints was investigated via two approaches namely parameter variation and heat treatment process. The tool rotational speed was varied between 600 and 1200 rpm, and the as-welded joints were subjected to both solution heat treatment and ageing for 1 h (at 520 °C) and 18 h (at 165 °C) respectively. The tensile-shear, peel, and cross-tension loads of the as-welded and heat-treated AA6061-T6/AA5754-O joints were studied while their respective microstructures and fracture behaviors were examined. The results show that undesirable unbonded and partially bonded regions are reduced in the joints due to the improved material flow, intermixing, and metallurgical bonded regions in the joints as the tool rotational speed is increased. The cross-tension, peel, and tensile-shear loads of the joints improved from 2499 to 3012 N, 2212–2712 N, and 5198–6429 N respectively as the level of the tool rotational speed is increased from 600 to 1200 rpm. The application of post-weld heat treatment on the as-welded AA6061-T6/AA5754-O joints is plausible due to the joint's improved failure loads attributed to the re-precipitation of strengthening phases within the joints. Up to 45% improvement in failure load is achieved in the heat-treated tensile-shear sample fabricated at 1200 rpm. •Undesirable unbonded and partially bonded regions are reduced in the joints due to the improved material flow, intermixing, and metallurgical bonded regions in the joints as the tool rotational speed is increased.•An increment in the tool rotational speed improves the cross-tension (2499–3012 N), peel (2212–2712 N), and tensile/shear (5198–6429 N) loads of the MFSC AA6061-T6/AA5754-O joints.•Heat treatment further improved the failure loads of all the joints with the tensile-shear samples improved by 17% and 45% at 1000 and 1200 rpm respectively due to re-precipitation of the strengthening phases.