Aluminum/steel dissimilar material with high interfacial strength manufactured by additive friction stir deposition

Dissimilar metallic materials find broad applications owing to the possibility of integrating multiple functions. However, the joining interface is a vulnerable site for failure in service. The design of high-strength bonding of dissimilar materials has been urgently needed. This study showed that a combination of additive friction stir deposition coupled with post-processing annealing enables the formation of a continuous Mg/O-enriched amorphous layer dotted with nano-rivet structures at the aluminum (Al)/steel interface. As a result, a high bonding strength (138.1 MPa) of Al/steel was achieved. We clarify the formation of discontinuous nano-rivet intermetallic compounds thanks to the AFSD-induced severe plastic deformation and local chemical reaction upon annealing, and we demonstrate the highest bonding strength is achieved at the size of nano-rivet compounds of ~200 nm and the aspect ratio ~ 0.5. Our findings provide a simple but versatile strategy to reverse the adverse effects of intermetallic compounds on the interface strength of dissimilar materials.