Influence of copper interlayer on the interface characteristics of stainless steel-aluminium transitional structure in wire arc directed energy deposition

Purpose The purpose of this study is to investigate the deposition of SS-Al transitional wall using the wire arc directed energy deposition (WA-DED) process with a Cu interlayer. This study also aims to analyse the metallographic properties of the SS-Cu and Al-Cu interfaces and their mechanical properties.Design/methodology/approach The study used transitional deposition of SS-Al material over each other by incorporating Cu as interlayer between the two. The scanning electron microscope analysis, energy dispersive X-ray analysis, X-ray diffractometer analysis, tensile testing and micro-hardness measurement were performed to investigate the interface characteristics and mechanical properties of the SS-Al transitional wall.Findings The study discovered that the WA-DED process with a Cu interlayer worked well for the deposition of SS-Al transitional walls. The formation of solid solutions of Fe-Cu and Fe-Si was observed at the SS-Cu interface rather than intermetallic compounds (IMCs), according to the metallographic analysis. On the other hand, three different IMCs were formed at the Al-Cu interface, namely, Al-Cu, Al2Cu and Al4Cu9. The study also observed the formation of a lamellar structure of Al and Al2Cu at the hypereutectic phase. The mechanical testing revealed that the Al-Cu interface failed without significant deformation, i.e. < 4.73%, indicating the brittleness of the interface.Originality/value The study identified the formation of HCP-Fe at the SS-Cu interface, which has not been previously reported in additive manufacturing literature. Furthermore, the study observed the formation of a lamellar structure of Al and Al2Cu phase at the hypereutectic phase, which has not been previously reported in SS-Al transitional wall deposition.