Role of Various Tool Pin Profiles in Friction Stir Welding of AA2024 Alloys

In FSW, tool pin profile has a significant contribution on mechanical and microstructural properties of metallic joints. In the present work, various pin profiles such as conical, pedal, cylindrical with thread, triangular, square and pentagonal pins are used to join the AA2024 plates. Mechanical and microstructural characterization is done for welded plates using different pin profile tools. The mechanical properties such as percentage elongation, ultimate tensile strength (UTS), microhardness and impact strength are significantly improved, when plates are joined using square pin profile. The obtained joint efficiency is 78% using square pin profile tool. The percentage elongation, UTS and impact energy of joint made by square pin tool are measured as 15%, 362 MPa and 5.7 Joule, respectively, which are higher than the values obtained using other pin profiles. EBSD analysis was performed to know the microstructural changes, which are a cause of mechanical properties alteration. Analysis reveals that stirred zone exhibits the recrystallized fine grains with equiaxed structure, which is a result of dynamic recrystallization and heating during plastic deformation of the zone. Large fraction of HAGB is also observed in stirred zone, which is a cause of improved mechanical properties of the joint.