Nanosegregation of ternary Cr-Ni-Fe alloy deposits electrodeposited from a Cr³⁺-based bath

A laminar structure with nanosized segregation was observed in Cr-Ni-Fe alloy deposits electroplated in a Cr³⁺-based bath with Ni ²⁺ and Fe²⁺ ions. The formation of laminar structure could be attributed to the depletion of preferentially reduced ions, or cathodic polarization, adjacent to the cathodic surface. This nanosized segregation could be clearly observed with scanning-transmission-electron microscope in high-angle angular dark-field (HAADF) mode. A crystalline Fe-rich alloy deposit with a grain size of 4 nm can be achieved with an electroplating current density of 15 A dm^-2, whereas an amorphous Cr-rich alloy deposit was produced with 25 A dm^-2. Owing to the approach toward thermal equilibrium in the two-phase field, uphill diffusion took place in the Cr-rich alloy deposit during annealing at 500 °C, forming a Cr- and Fe-rich multilayer.