Evaluation of dissimilar metal joining of Al/steel by in-situ formation of a copper barrier interlayer

The utilization of pure copper powder as a filler material in dissimilar metal laser welding of Al/steel was investigated in this study. The microstructure and tensile properties of the welded joint were analyzed, and the thermodynamics of microstructure formation within the weld zone were discussed. The results revealed that pure Cu powder successfully facilitated the in-situ formation of a barrier interlayer between aluminum and steel, effectively impeding the generation of Fe-Al intermetallic compounds. Notably, the weld zone near the Al base metal exhibited a eutectic zone comprising alpha-Al + Al2Cu eutectic structures, along with a thin layer of Al4Cu9 phase. Consequently, the dissimilar joint achieved a well-formed weld and exhibited a tensile strain capability of similar to 6 %, with the fracture occurring in the Al base metal.