Solid-state additive manufacturing of structurally robust and bondable copper coatings on aluminum substrates

This study presents a solid-state additive manufacturing strategy for fabricating high-density, electrically conductive copper (Cu) coatings on aluminum (Al) substrates using the cold spray additive manufacturing (CSAM) process. Significant enhancements in coating density, electrical and thermal conductivities, and interfacial bonding strength were observed with increasing inlet gas temperature and pressure, attributable to more effective plastic deformation and resultant dynamic recrystallization. By optimizing the inlet gas temperature and pressure to 1000 °C and 50 bar, respectively, Cu deposits with properties approaching those of bulk Cu—including an electrical conductivity of 98 % IACS and a thermal conductivity of 384 W·m⁻¹·K⁻¹—were successfully achieved. Simultaneously, interfacial bonding strengths exceeding 50 MPa were achieved without the need for post-deposition heat treatments. Microstructural analyses revealed that elevated inlet gas conditions promoted dynamic recrystallization within the Cu coatings and facilitated diffusion bonding with the Al substrate through the formation of intermetallic compounds. Furthermore, localized thermal input from the deposition process induced partial recovery within the Al substrate, resulting in a chemically and mechanically stable CuAl interface with minimal residual stress. These findings demonstrate that the CSAM process enables the deposition of robust, bulk-like Cu layers on Al in the as-sprayed state, offering a scalable, cost-effective, and geometrically versatile alternative to conventional cladding techniques. This study addresses key challenges in CuAl joining and paves the way for the broader application of Cu coatings in high-performance, lightweight structural and electrical components.