Process parameter optimisation in pinless friction stir spot welding of dissimilar aluminium alloys using Multi-start algorithm

Abstract

Friction stir spot welding, a solid-state metal joining process has been utilised to join dissimilar aluminium alloys using pinless tools. The optimal welding conditions were predicted using the Multi-start algorithm with 25 starting points and were validated by confirmation tests. The Multi-start algorithm predicted the maximum tensile shear force of 6.28 kN at the tool rotational speed of 841.83 r/min, plunge depth of 0.618 mm, shoulder diameter of 24.99 mm, plunging speed of 0.04 mm/s and dwell time of 8 s. The scanning electron microscopy analysis revealed the formation of flatter hooks in the weld zone. The electron backscatter diffraction scans revealed a decrease in grain size at the lower sheet (Al 5754) due to the action of 30 kN axial force during pinless friction stir spot welding. Two different modes of fracture were observed: (i) nugget pull-out with necking; (ii) shearing. The fracture modes were observed to be dependent on the process parameters like shoulder diameter and plunge depth.

[Retracted] Improvement on Mechanical Properties of Submerged Friction Stir Joining of Dissimilar Tailor Welded Aluminum Blanks

“…e tensile test samples of failed at the weld zone indicating the nugget zone is not in contact with the submerged medium during FSW which resulted in formation of a weaker zone at the nugget region [12]. e tensile strength of the underwater tensile welded samples tends to decrease with increase in tool rotational speed that increases the temperature at the weld zone which resulted in grain growth in the weld zone; hence, the drop in tensile strength is observed [25,26].…”

Enhancement of Mechanical Properties on Novel Friction Stir Welded Al-Mg-Zn Alloy Joints Reinforced with Nano-SiC Particles

“…The minimum hardness value was found at HAZ. The hardness at the HAZ is minimum due to precipitation phenomena [36]. The less hardness observed in the HAZ is due to the fact that IMCs may form Mg 2 Si and less Si compound on the Al-Mg-Zn/1 wt% nano-SiC (sample 1).…”

Effect of surface oxide layers in solid-state welding of aluminium alloys – review

“…The only difference was in the shape and size of hook defects which can be correlated to tool geometry. Those defects combined with a keyhole in the middle of the joint significantly reduce the mechanical properties of the joints which were one of the main reasons to seek different solutions such as FSSW with pin-less tool [105][106][107] or novel methods such as refill FSSW [108][109][110][111].…”