Abstract:Defect-free butt joints of 3003 Al alloy to mild steel plates with 3 mm thickness were performed using friction stir welding (FSW). A heat input model reported for similar FSW was simplified and used to investigate the effects of welding speed, rotation speed and tool shoulder diameter on the microstructure and properties of dissimilar welds. The comparison between microstructure, intermetallics and strength of welds shows the good conformity between the results and the calculated heat input factor (HIF) achieved from the model. The joint strength is controlled by Al/Fe interface at HIF of 0.2-0.4, by TMAZ at HIF of 0.4-0.8 and by intermetallics and/or defects at HIF>0.8.

Key words: friction stir welding; dissimilar joining; microstructure; tensile strength; aluminum alloy; carbon steel; intermetallic compound