Mechanical and corrosion responses of Al/Mg dissimilar submerged friction stir welded joints

The demand for Al/Mg composite structures in portable electronics has been increasingly urgent, yet Al/Mg composite structures face significant challenges of low strength and poor corrosion resistance. In this paper, friction stir welding (FSW) was utilized to address these issues with a focus on the mechanical properties and corrosion behavior. Submerged FSW successfully facilitated the formation of a dense, defect-free interface with superior mechanical interlocking, primarily attributed to the suppressed heat input during welding and the enhanced material flow within the joint region. Under the submerged conditions, the ultimate tensile strength of the welds showed a trend of initial increase followed by a decrease as rotational velocity increased. The ultimate tensile strength of 171 ± 4 MPa (71.3% of AZ31B base metal) was attained at 800 rpm. Electrochemical characterization revealed distinct corrosion resistance, with the 6061 Al alloy base metal showing the best performance, followed by the AZ31B Mg alloy base metal, with micro-galvanic effects accelerating degradation in the severe plastic deformation zone. The corrosion resistance of the joints was found to be inversely proportional to the rotational velocity.