Interface strengthening in dissimilar double-sided friction stir spot welding of AZ31/ZK60 magnesium alloys by adjustable probes

Dissimilar welding of AZ31/ZK60 magnesium alloys with a thickness of 2 mm was successfully carried out by the double-sided friction stir spot welding with adjustable probes. A dissimilar joint bearing flat surfaces on both sides without a keyhole was obtained and the shear failure load of 8.7 +/- 0.5 kN was reached. The role of the adjustable probes has been revealed in detail. In the center of the stir zone, the welding interface structure was heterogeneous around which some distinct oxides still remained, leading to a weak interface strength. On the contrary, the welding interface structure around the shoulder/probe interface was homogeneous with no oxides giving rise to a strong interface strength, which is attributed to the severe material flow introduced by the adjustable probes. In addition, the vicinity outside the shoulder/probe interface, where the fracture occurred during the shear tensile tests, was also strengthened owing to the shearing and torsion by the adjustable probes. Therefore, a stable plug failure can be obtained and the joint properties can be improved. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

In this study, dissimilar welding of AZ31/ZK60 magnesium alloys was successfully achieved using double-sided friction stir spot welding with adjustable probes, resulting in a strong joint with improved properties.