Double Stage Friction Stir Spot Extrusion Welding: a Novel Manufacturing Technique for Joining Sheets

A Novel Technique is proposed in this investigation called Double Stage Friction Stir Spot Extrusion Welding (DSFSSEW). It is carried out in two stages by using a pin-shoulder tool in step 1 and a pin-less tool in step 2 to investigate the joint strength of the AA1050 sheet. The advantage of this new double-stage FSSEW technique compared to the classical FSSW led to the elimination of the keyhole, which is an intrinsic flaw of the Friction Stir Spot Welding (FSSW) process resulting in higher mechanical joint properties. The impact of the plunge depth and tool revolving speed on the characteristics of the bond was investigated. The height of the extruded aluminium was increased by increasing the tool rotation speed and the plunging depth which was the effective variable. The joint strength was increased in step 2. The two sheets are bonding together at a line of the interface by a mechanical interlock formed by a continuous metal flow of aluminium extrusion that is free of flaws. There were two mechanisms of failure in the studied samples: cleavage of the aluminium metal at the tool trace and shearing of the extruded aluminium, respectively. The suggested method is novel and has a great potential for future investigation, this work might pave the way for studies of welding with additional alloys, both similar and dissimilar to those already studied.