Mechanisms of enhanced ductility in cold spray additive manufacturing of copper

Cold spray additive manufacturing (CSAM) enables rapid, large-scale fabrication of metallic components in the solid state. However, achieving high ductility remains a major challenge due to weakly bonded particle interfaces. Here, we elucidate the mechanisms governing ductility in CSAM copper by integrating atomic-scale characterisation with first-principles simulations. The negligible ductility of as-sprayed copper arises from Cu 2 O nanocrystals, oxygen clustering, and nanopores at particle interfaces, which collectively introduce a pronounced shear modulus mismatch, heterogeneous strain distribution, and pore-driven fracture. Annealing reconfigures these nanoscale interfacial features through oxygen surface segregation and partial nanopore closure, promoting oxygen-depleted metallic bonding regions and substantially enhancing ductility. We further show that an interfacial cohesion index quantitatively correlates the interfacial bonding state with macroscopic ductility. These results establish quantitative links among interfacial chemistry, porosity evolution, and uniform plastic deformation, providing a mechanistic framework for engineering ductility in cold-sprayed metals and for optimising the mechanical performance of components produced by solid-state additive manufacturing.