Double side friction stir welding of AA6061-T6 alloy plates: microstructure, mechanical properties and corrosion resistance of joints

In this research, the double side FSW technique is used to join the AA6061-T6 base plates with different rotational speed to study the process parameters effect on the welded structures. The Tool Rotational Speed (TRS) is set at 800 rpm, 1000 rpm, and 1200 rpm while maintaining a consistent tilt angle (2°) and traveling speed (20 mm/min). The tensile strength properties were evaluated by conducting uni-axial test on double side specimens. The micro-hardness measurement was performed across transverse direction to study the effect of rotation speed. To study the corrosion rate at the weld zone, the sample was tested using cyclic sweep test. The optical and scanning electron microscopes were used to study the structural changes in various zones. Also, the phase changes and segregation of alloying elements were analysed using X-ray diffraction analysis. The tensile stress of 168 MPa was observed in TRS-1200 joint at greater speeds and exhibiting the optimal combination of strength and ductility. The micro-hardness profiles across the weld zones exhibited clear variances, with the nugget zone demonstrating increased micro-hardness as a result of its small grain structures. TRS-1200 joint exhibited a corrosion rate of 0.0131563 mm/y, which was marginally greater than the base metal. The scanning and optical metallography investigations showed that there was a noticeable reduction in grain size in the nugget zone. The XRD examination verified the existence of a distinct face-centered cubic structure in the weld zone. It results in joints that have improved mechanical properties and satisfactory resistance to corrosion.