Formation mechanism of intermetallic compound at the weld interface of dissimilar friction stir welded joint of pure aluminum and mild steel

There is considerable interest in joining of aluminum to iron because of various advantages such as weight reduction of vehicles. However, the intermetallic compound (IMC) formed at the welded interfaces causes a brittle fracture of the dissimilar joint. Therefore, it is important to prevent the formation of IMC. It is well-known that friction stir welding (FSW) is suitable for the inhibition of IMC formation due to the low heat input. This study investigated the formation mechanism of IMC during FSW by comparing the results from previous studies, in which dissimilar welds were prepared by the diffusion bonding and roll bonding. The time compensated IMC thickness in FSW was larger than that in the other joining methods. This is because three factors of fresh surface, stored strain and plastic flow were strongly affected the formation mechanism of IMC. However, the amount of IMC was significantly small because the welding time was very short. It is therefore considered that a dissimilar joint of aluminum to iron can be achieved by FSW.