Effect of Square Pin Tool on Friction Stir Welded AA 6061-T6 from the Perspective of Revolution Pitch

Abstract

The phenomenon of revolution pitch was studied on AA 6061-T6 with a square pin tool for friction stir welding (FSW). The tool rotational speed and traverse speed were varied at four levels and selected in a manner so that the revolution pitch could comprise both lower and higher magnitude of variation when compared among them. An attempt was made to investigate the material flow from the macrostructure of both vertical (transverse to welding direction) and horizontal (parallel to the weld surface) cross-section. The study showed a significant amount of variation in terms of spindle torque, forces, material flow, and tensile properties. The increased material flow was noticed in the top surface of the weld from advancing to the retreating side at increased revolution pitch. Whereas an increased material flow was observed in the downward direction through the retreating side of the nugget. At increased revolution pitch a clear division in the onion ring was noticed towards the retreating side. The variation of torque, force and material flow showed a consistent trend for a higher change in revolution pitch. As the revolution pitch increased finer nugget grains were obtained causing increased tensile properties.

Key-words:
Friction stir welding; Revolution pitch; Material flow; Square tool