INFLUENCE OF A TOOL’S ROTATIONAL SPEED ON THE MECHANICAL PROPERTIES OF FRICTION-STIR-WELDED JOINTS OF DISSIMILAR AA6082 AND AA5052 ALUMINIUM ALLOYS

This study examines the influence of a tool’s rotational speed on the microstructure and mechanical properties of dissimilar friction-stir-welded joints of AA6082 and AA5052 aluminium alloys. The joining process was carried out at various rotational speeds of 600 min–1, 1000 min–1, and 1400 min–1 and a constant welding speed of 35 mm/min using a high-speed-steel (HSS-Co5) tool with a cylindrical pin. The microstructure of the welded joints was characterized using optical microscopy. The Vickers microhardness, tensile properties, and impact strength of welded joints were evaluated and compared to base metals. Results showed that the mechanical properties and the joint performance were considerably influenced by the tool’s rotational speed due to the amount of heat input and the formation of macroscopic defects in the stir zone. It was found that a rotational speed of 1000 min–1 is the suitable welding parameter for optimum mechanical properties. The welded joint at 1000 min–1 shows a tensile strength of 122 MPa, elongation of 8.1 %, specific impact strength of 0.43 J/mm2, and a maximum microhardness of 75 HV in the stir zone. In all welded joint samples, the fracture locations were near the edge of the welded zone on the retreating side. The results provide further insight into the appropriate selection of FSW process parameters that ensure excellent joints between AA5052 and AA6082 alloys with the required mechanical properties.