Mechanical Evaluation and Microstructure of Friction Stud Welded Aluminium–Mild steel Joints

Friction stud welding of dissimilar metals has a variety of applications in the field of aerospace, automotive, nuclear engineering. Especially, in the field of automobile engineering, there is a requirement of joining a mild steel earthing pin to an aluminium car body. Hence, in this study, joining of aluminium (AA 6063) and mild steel (AISI 1030) was successfully carried out by friction welding technique. Experiments were conducted by varying friction time, and axial shortening distance and impact strength were measured. Macro and microstructural investigation was carried out using optical microscope, scanning electron microscope and energy dispersive X-ray analysis. Microhardness measurement shows increased plastic deformation of aluminium at the interfacial region. Optical micrograph reveals a dark region of about 240μm consisting of dynamic recrystallized grains on the aluminium side very near to the interfacial region. SEM micrograph and EDX analysis shows the presence of iron oxide on the aluminium side along with the formation of inter metallic compound FeAl at the joint interface. Hardness measured at the weld line is found to be higher than the hardness of the base metal due to increased plastic deformation.