Microstructural and mechanical characterization of a dissimilar friction stir welded butt joint made of AA2024-T3 and AA2198-T3

• Two separate regions are identified in the nugget of the weld.
• Similar types of crystallographic texture are generated inside the nugget for both materials.
• In tensile test, strain localization happed in the low hardness region between nugget and softer base material.
• Satisfactory butt welds can be produced in terms of strength.

The aim of this investigation is to evaluate the microstructural features, material flow, and postweld mechanical properties of a dissimilar joint made of AA2024-T3 and AA2198-T3 produced by friction stir welding. First of all, this work presents a microstructural analysis by multiscale observations of the joint (i.e. macro- and micrographs). Then, the mechanical properties based on hardness measurements, residual stress analysis, and tensile tests are documented. Overall, the results show that satisfactory butt welds can be produced with these two alloys even when full mixing of the two alloys was not achieved in the nugget region. The weakest region of the joint is the heat affected zone of the AA2198 alloy.