Expanding-welding: A hybrid deformation and welding process for joining dissimilar metals

To achieve ultra-strong joint performance and high processing efficiency of joining dissimilar metals, a novel hybrid process, Expanding-Welding method (EW), was proposed. EW effectively combined metallurgical bonding and mechanical expanding effects in a single process. To demonstrate its effectiveness, EW was applied to join aluminum tube to steel tube-sheet hybrid structure. Molecular dynamics analysis showed that the Al/Fe diffusion coefficient was increased by 2 orders of magnitude under the compression and shear condition. Severe plastic deformation introduced by the welding tool induced rapid atom diffusion behavior, and the thickness of the diffusion layer reached 9.5 ± 0.4 µm. The maximum joint pull-out strength was 176.5 ± 13.7 MPa, reaching 73.5% of that of base Al alloys. The success of this hybrid deformation-welding process can increase energy efficiency in many industrial sectors, such as constructing reliable tube-to-tube-sheet structures with dissimilar metals for heat exchangers in the field of petroleum and chemical industries. • As a hybrid deformation and welding process, Expanding-Welding method was effective to join dissimilar metals. • Aluminum tube to steel tube-sheet structure was joined, which had application potential for heat exchangers. • Severe plastic deformation induced atom rapid diffusion at Al/Fe interface with compression and shear. • The pull-out strength 176.5 ± 13.7 MPa reached 73.5% of base Al alloys, showing excellent mechanical joint performance.