Process optimization of friction stir spot welding-soldering for aluminum/steel dissimilar materials and mechanical properties of the joints

DP590 steel and 6061 aluminum alloy were welded by large-diameter friction stir spot welding without needle. The mechanical properties of the aluminum-steel welded joint were measured through shearing test,and the fracture morphology was observed by SEM and EDS. The results showed that the anti-shear force of the joint reached 13. 24 kN when the stir head rotation speed,pressed depth and dwell time were 1 000 r/min,0. 2 mm and 90 s,respectively. The Al-Zn brazing filler metal can help to wet the aluminum-steel weld interface,prevent the oxidation of the interface,and facilitate the metallurgical bonding formation between Al and steel. As a result,the anti-shear force of the aluminum-steel joint is improved.