Effect of the static shoulder on microstructural,textural,and mechanical characteristics during friction stir welding of Al6061

Abstract

In the present investigation, a novel static shoulder friction stir welding (SSFSW) tool has been designed and fabricated. The designed tool works both as rotating shoulder FSW (RS-FSW) and SSFSW. To evaluate the effectiveness of the developed tool, Al6061 plates have been subjected to both RS-FSW and SSFSW using the indigenously developed tool. The microstructure evolution, axial force, texture development, and mechanical properties were evaluated and compared for both RS-FSW and SSFSW. Adequate heat generation in SSFSW resulted in a homogeneous structure at the stir zone. Electron back scattered diffraction analysis demonstrated the presence of red-colored regions along the grain boundaries indicative of more dislocation density. These regions acted as preferable sites for precipitate (Mg₂Si) accumulation, which greatly affected the mechanical properties of the joint. SSFSW joints contained a strong {111} texture of R-cube and S component with a maximum intensity of 6.85, while RS-FSW joints contained A and A* components with a maximum intensity of 4.85. The hardness plots showed a wide lower hardness region in RS-FSW with a maximum hardness of 101HV and 110HV (SSFSW). During the tensile test, both the joints failed in the lower hardness region after achieving 88% (SSFSW) and 75% (RS-FSW) strength of base material.