Role of welding parameters on interfacial bonding in dissimilar steel/aluminum friction stir welds

In this study, lap welds between Al5754 to DP600 steel (aluminum plate top, and steel plate bottom) were manufactured by friction stir welding (FSW). The effects of welding parameters (i.e. travel speeds and penetration depth into lower steel sheet) on the interfacial bonding, tensile strength, and failure mechanism were investigated. The results show that intermetallic compound of Fe4Al13 was detected at the Al/Fe interface. The weld strength increases significantly by increasing the penetration depth into the lower steel substrate at all travel speeds. The failure mode under overlap shear loadings is premature failure through the aluminum substrate when the penetration depth is more than 0.17 mm, and shear fracture when the penetration depth is less than 0.17 mm.