Pin plunging reinforced refill friction stir spot welding of Alclad 2219 to 7075 alloy

Abstract

Abstract A Pin-plunging reinforced refill friction stir spot welding (P-RFSSW) technique was introduced in this study in order to solve the problem of the central void defect and the alclad residues in the weld center associated with conventional refill friction stir spot welding (C-RFSSW) of dissimilar alclad aluminum alloys. The P-RFSSW process is based on promoting the plastic deformation in the weld center owing to the addition of an initial pin plunge stage. The microstructure and mechanical properties of the C-RFSSW and P-RFSSW joints were compared. Results have shown that the P-RFSSW process could eliminate the central void defect and promote the metallurgical bonding and intermixing in the weld. Weld strength was improved when using P-RFSSW compared with the C-RFSSW process, which was attributed to the specific downward extended hook defect into the stronger, thicker 7 series aluminum alloy.