Effect of electrolyte temperature on composition and phase structure of nanocrystalline Fe-Ni alloys prepared by direct current electrodeposition

Composition and phase structure were analyzed using electron microprobe and X-ray diffraction for a series of Fe-Ni deposits prepared by direct current electrodeposition at four electrolyte temperatures of 298, 313, 333 and 353 K. The well-known anomalous codeposition became less significant with increasing electrolyte temperature. and the deposition eventually shifted to an equilibrium mode in which the electrolyte composition was approximately equal to the deposited one at 353 K. The phase structures of the deposits were affected significantly by the electrolyte temperature. At 298 K, the resultant phases of the deposits were very similar to those of the quenched bulk alloys with the same composition. On the other hand, the 353 K deposits contained phases similar to those of the bulk alloys cooled slowly from high temperatures. The great enhancement of the thermodynamic equilibrium is attributed to the increase of the surface mobility of the adatoms/monovalent intermediates with increasing electrolyte temperature. (C) 2012 Elsevier B.V. All rights reserved.