Effects of Friction stir Welding Parameters on Microstructure and Mechanical Behavior of Dissimilar Joint of 7075-T6 Aluminum and Alpha Brass

Abstract

This study examines the microstructure and mechanical properties of dissimilar joints of 7075-T6 aluminum and brass alloy fabricated by friction stir welding. Effects of travel speed and pin offset on microstructure, microhardness, and tensile strength of the welded joints were investigated. Results of different tests indicate that there was a longitudinal crack in samples welded at the low tool offset, on the other hand in the offsets higher than 0.8, the welding quality decreases due to the mechanical forge reduction. The maximum tensile strength obtained for the joint was equal to %72 of the tensile strength of the brass base alloy which was fabricated at travel speed and offset of 12.5 mm.min-1 and 0.8 mm respectively. Microstructure of the samples was observed by the optical microscopy. Thickness and chemical composition of the intermediate layer was examined by scanning electron microscopy (SEM) equipped with an EDS unit. Specimens were then characterized by X-ray diffraction (XRD) to investigate the phase constituent of the intermediate layer. It was found that an increase in the thickness of the intermediate layer could decrease the tensile strength of the joint.