Joining of high-strength dual phase steel to aluminum is essential in transportation industry. FSW as one of the best available methods for doing so, has challenges. First, FSW tools need to be made of high-strength and hard carbide-tungsten materials which are very expensive and fail frequently during FSW due to their brittleness. Second, formation of intermetallic compounds (IMCs) degrades thejointsmechanicalproperties.Third,FSWneedstobeperformedinlapcon¿gurationwhichadds weight and limits the application of the joint. In the present study, buttering technique was used to overcome all these issues. The faying surface of dual phase steel was layered with SS316L before FSW to aluminum. By doing so, simple and cheap FSW tool made of H13 steel was successfully usedtojointdualphasesteeltoAA6061-T6inbuttcon¿guration.Ajointstrengthof500MPawas achieved owing to ultra-thin and non-continuous IMCs at the joint interface. The islands of Al-Fe IMCs were dispersed at the interface with size less than 1 micrometre, while the rest of the interface was free of IMCs. This caused a mixed fracture mode of the joints (brittle and ductile) through the interface during tensile testing. The results of the present study can be used for joining hard-to-weld materials by FSW in industry.
