Enhancement of Tensile and Microhardness of AA 6082-T6 Friction Stir Welds via Brass Interlayers

Abstract—This paper investigates the effects of brass interlayer on the microstructural and mechanical properties of friction stir welded AA 6082-T6. To analyze the reaction and distribution of brass interlayer with the aluminum alloy in the stir zone, scanning electron microscopy (SEM) and optical microscopy were used. X‑ray diffraction (XRD) analysis was used to examine the phase composition. Tensile and microhardness testing was performed to investigate the mechanical properties. The results showed that with brass interlayer, the joint’s tensile strength increased to ~33% compared to joints without interlayer. The microstructural analysis indicated that the brass interlayer dispersed very well at the stir zone, which can be observed through the optical image. At the nugget zone, the mixing of brass with the aluminum matrix can be observed, which results in the formation of intermetallic compounds (IMCs). Fractography investigation of the fractured tensile specimen indicates pure ductile fracture in Al–Al joints shifted towards brittle fracture due to the formation of IMCs in the joints with a brass interlayer. In summary, it can be concluded that the use of brass interlayer is an effective way to overcome the softening issue in friction stir welding of similar aluminum alloys.