Influence of Tool Shoulder Concave Angle and Pin Profile on Mechanical Properties and Microstructural Behaviour of Friction Stir Welded AA7075-T651 and AA6061 Dissimilar Joint

In this present study, an attempt has been made to investigate the influence of tool shoulder concave angle and pin profile on mechanical properties and microstructural behaviour of friction stir welded AA7075-T651 and AA6061 dissimilar joint. The concave profile tool shoulder with three different angles of 1.5°, 3° and 4.5° was employed. Besides, three different pin profiles like straight cylindrical, square and triangular were used to fabricate the FSW joints. The concave shoulder angle regulates the frictional heat, and the tool pin profile enhances the material flow to improve the mechanical properties of the joint. From this work, it was found that 3° concave shoulder profile with square pin exhibits the maximum tensile strength, hardness and bending angle of 298 N/mm 2 , 143 Hv and 49°, respectively. The pulsating stirring action of the square tool pin exhibits ductile fracture, and it is evident from the presence of fine dimples.