Effect of Tool Travel Rate on Microstructure Evolution and Mechanical Properties of Dissimilar Friction Stir Welded Joints of AA7075 and AA6061 Aluminium Alloys.

The current research aims to investigate how processing parameters influence the mechanical properties and microstructure development of dissimilar AA7075/AA6061. These alloys were friction stir welded (FSWed) at varied traverse rates (ranging from 20 to 60 mm/min) while maintaining a constant rotation rate of 708 rpm. Several characterization techniques, such as electron microscopy and optical microscopy, were utilized to quantify the microstructure evolution of these dissimilar FSWed joints. A universal testing machine and a Vickers microhardness tester were used to evaluate the mechanical characteristics. The field emission–scanning electron microscope was used to examine the fracture surfaces of the fractured tensile specimens. The experiment revealed that the grain size within the nugget zone decreased as the tool traverse rate increased from 20 to 60 mm/min. Specifically, the grain size in the nugget zone measured 5.82 µm at a speed of 20 mm/min, whereas it reduced to 3.64 µm at 60 mm/min. Furthermore, the FSWed sample processed at 60 mm/min demonstrated a superior ultimate tensile strength of 251 MPa. The hardness values exhibited a similar increasing trend as the traverse speed increased. The heat-affected zone of the AA6061 side achieved the lowest hardness at a traverse rate of 20 mm/min. A ductile fracture mode predominated for most of the dissimilar joint fracture surfaces investigated. [ABSTRACT FROM AUTHOR]