Effect of pin length on Friction Stir Spot Welding (FSSW) of dissimilar Aluminum-steel joints

Abstract

Friction stir welding (FSW) has produced a great impact in several industries due to the advantages that this process presents. In particular, the automotive industry has developed a variant of the original process, called Friction Stir Spot Welding (FSSW), which has a strong interest related to the welding of aluminum alloys and dissimilar materials in thin sheets. Aluminum-steel welding is an actual challenge, being FSSW an alternative to produce these joints. However, the information available related to the influence of process parameters on the characteristics of aluminum-steel joints is scarce. The aim of this work was to study the effect of the pin length of the welding tool and its penetration depth, during friction stir spot welding (FSSW) of overlaps joints of AA6063 with galvanized low carbon steel. FSSW was done by changing the pins length between 0.65 and 1.5 mm, and also by modifying the tool penetration depth in the welded joints. On the welded spots macro and microstructural characterization was performed, Vickers microhardness profiles were determined and Peel and Cross Tension Tests were also done. The maximum loads increased when the tool penetration depth goes up and the pin length decreased. The fracture mode was, at first, interfacial meanwhile it changed to a circumferential mode when the tool penetration depth increased and the pins length was reduced.