Alloying-modulated strengthening behavior of Cu–xAg/Ni multilayer systems

Abstract Cu–xAg/Ni multilayers ( x = 0 at.%, 5 at.%, 10 at.%) with individual layer thickness of 25 nm were synthesized to explore alloy-modulated strengthening effects in nanolayered composites. Nanoindentation measurements revealed that alloying the Cu layers with 5 at.% and 10 at.% Ag increases the hardness of the Cu/Ni multilayer system by 10.4% and 12.9%, respectively. Microstructural characterization indicates that the solid solution of Ag atoms in the Cu matrix leads to lattice expansion and a corresponding increase in lattice mismatch at the Cu–xAg/Ni interfaces. Additionally, nanoscale Ag-rich precipitates were observed, resulting from the partial demixing of Ag in the Cu–Ag layers. The enhanced mechanical strength is attributed to a combination of strengthening mechanisms, including solid solution strengthening, precipitation hardening, and interface strengthening. Among these, theoretical analysis identifies lattice misfit strengthening at the interface as the predominant contributor to the overall hardening effect. Graphical abstract