Recoverable tuning of lattice mismatch and strength in ultrastable-nanostructured Cu/Ag spinodoid alloys

Abstract

The strengthening effect of interface in materials is usually studied by monitoring the change of strength in response to varying structure sizes, such as the varying grain or phase sizes. In this study, we demonstrate that the strength of a nanostructured material can be recoverably tuned by modifying interfacial structure without changing structure size. Specifically, we studied the Cu/Ag spinodoid alloys fabricated by dealloying and electrochemical deposition, which exhibit a cube-on-cube orientation relationship between two interpenetrating nanophases. This material remains stable against coarsening even at temperatures near the eutectic melting point, due to the presence of low-energy semi-coherent interfaces and the lack of defects such as grain boundaries. Using cyclic thermal annealing, we are able to alter the solid solubility of both nanophases and, consequently, the lattice mismatch between them, resulting in a recoverable tuning of hardness and strength. The amplitude of hardness modulation decreases with increasing feature size (λ), and changes sign when λ exceeds ∼500 nm. This is attributed to a competition between two strengthening mechanisms: the interface-induced strengthening that is more prominent at a lower λ, and the solid solution hardening that is largely λ-insensitive. The finding indicates that interface hardening prevails over solution hardening when λ is below ∼500 nm. Current study paves the way for the development of strong and stable nanostructured materials whose properties can be optimized by independently tailoring feature sizes and interfacial structures.