Interfacial uniformity control of Al/steel butt joint via rotating laser-GMAW hybrid welding-brazing

The excessively hard and brittle steel-aluminum(Fe-Al) intermetallic compounds (IMCs) have adverse effects on the performance of Al/steel dissimilar material joining, even degrading their mechanical properties seriously. For this, most sound Al/steel butt welded-brazed dissimilar joints were achieved via this rotating laser-GMAW welding technique in the present study, in which the formation of Fe-Al IMCs was effectively suppressed by adding the additional alloying element Si, and the interfacial structure was effectively controlled by inserting a rotating laser, respectively. The detailed effect process of the Si element and the rotating laser was investigated in terms of Finite element analysis, interfacial structure, and the changed mechanical properties. The results indicated that the temperature distribution at the interface was adjusted based on the rotating laser beam, achieving the uniform distribution of the interfacial temperature. Moreover, the addition of Si elements enabled the formation of Al-Si-Fe IMCs at the interface, thereby replacing the original Fe-Al IMCs. Finally, a uniform brazing interface layer composed of a single τ 5 -Al 8 Fe 2 Si phase was formed at the final Al/steel interface under the combined effect of these two factors. When the rotating laser beam diameter was 2.0 mm, optimal thickness uniformity was observed. At this time, the tensile strength of the joint reached 218 MPa, approximately 75 % of the Al base metal.