Interfacial microstructure and mechanical properties of Al/steel joints fabricated via thermo-compensated resistance brazing welding with cold spray Zn interlayer

Achieving the effective joining between Al alloy and stainless steel with a large cross-section was meaningful in the significant industry field. For this, the Al/steel dissimilar bimetal materials were manufactured by a novelty hybrid technology, named thermo-compensated resistance brazing welding. The effect of the single Zn foil and the deposited Zn coatings with cold spray technology on the bonding interface, interfacial microstructure, and mechanical properties of the final Al/steel resultant joints were systematically investigated by the relevant analysis method. The results revealed that the obvious reaction layer with main components of Al(s.s) was formed at the Al/steel joints with the single Zn foil as the interlayer. Meanwhile, the introduction of the Zn interlayer improved the temperature field of the joint, which enhanced the lap-shear load of the weld. Besides, the Zn coating was deposited at the top surface of the 304ss substrate as the interlayer to increase joint performance further. The advantage of the pre-deposition formed a better metallurgical bond between the coating and 304ss. The subsequent lap-shear load of the weld was improved with the increase of the Zn coating thickness. The maximum lap-shear load of the final joints reached 2087.6N with a Zn coating thickness of 500 μm and the interfacial structure of the joint was changed: Al alloy, reaction layer I, Al(s.s) + Al₂O₃, and 304ss from top to bottom. The main composition was Al(s.s) at the reaction layer I between Al alloy and coating.