The fabrication of Al/steel bimetallic structure by flux-coated cold metal transfer wire-arc additive manufacturing: Formability enhancement, interfacial microstructure and mechanical property

AbstractThe Al/steel bimetallic structure shows great potential in fabricating lightweight structures and transition joints. In this study, a coated flux is utilized to achieve steady processibility of Al/steel bimetallic structures by cold metal transfer wire-arc additive manufacturing. The effect of coated flux layer on macro morphology, formability enhancement, interfacial microstructure, mechanical property and fracture morphology of Al/steel bimetallic structures are analyzed. The result reveals that the introduction of flux layer can effectively dissolve and react dense oxide films on surfaces of high-temperature Al alloy molten pool, to promote reaction wetting between the dissimilar metals. Meanwhile, the flux can stabilize droplet transfer process and avoid random movement of cathode spots to guarantee good arc stiffness, therefore significantly achieving formability enhancement of Al/steel bimetallic structures. The interfacial reaction layer is identified as Fe-Al based reaction layer, the sufficient flux layer effectively promotes IMCs growth and will strengthen interfacial metallurgical bonding of Al/steel interface. The Al/steel bimetallic structures display excellent shear strength of not less than 70 MPa and tensile strength of 103.3 MPa, while the more deposition times will not affect shear strength of the bimetallic structure but resulting in slight tensile strength decline.