High ductility induced by twin-assisted grain rotation and merging in solid-state cold spray additive manufactured Cu

In contrast to fusion-based additive manufacturing (AM) methods, cold spray (CS) is a solid-state metal powder deposition process that has evolved from a traditional coating method to a novel AM technique, i.e. CSAM, for fabricating components and repairing damaged parts. In this study, we demonstrate that the long-standing low ductility of CSAM metallic deposits can be addressed through constructing a unique microstructure. A Cu deposit with 29.7% in elongation and 270 MPa in tensile strength has been produced using a proper spray parameter set. The high ductility of the Cu deposit originates from grain rotation and merging during tensile deformation, which is facilitated by twin boundaries acting as a bridge to dislocations slip. The understanding of high-ductility Cu deposits may help develop other high-strength and high-ductility CSAM metallic materials.