Microstructure Characterization and Tensile Behavior of Dissimilar Friction Stir Welded AA6082-T6 and AISI 409 Ferritic Stainless Steel

Dissimilar AA6082-T6 aluminum alloy and AISI 409 ferritic stainless steel (FSS) plates of 3-mm thickness were joined successfully via friction stir welding (FSW). The joints were made by varying the welding speed (20–100 mm/min) while the rest of the process parameters were unchanged. The interfacial microstructure features were observed through various microscopes, and the mechanical performance was tested. No defects, such as voids, were found in any of the joints. A portion of FSS material was broken and scattered in the stir zone as reinforcement particles. The welding speed greatly influenced the size and the dispersion of steel particles. A mixed material flow pattern was not found in the stir zone. The presence of an Al₃Fe intermetallic compound was spotted at the interface by XRD patterns. Fine grains were revealed in EBSD images. The stir zone was strengthened compared to aluminum side due to steel particles which provided a composite effect. The highest tensile strength of 205 MPa and elongation of 2.5% was obtained at 20 mm/min welding speed due to fine particle dispersion. All the jointed showed limited ductility.