PHASE STABILITY OF ELECTRODEPOSITED ALLOYS THE CASE OF IB METALS - Sn ALLOYS

摘要

In this work the phase structure of electrodeposited binary alloys of noble metals with Sn is considered and differences with respect to metallurgical alloys and their equilibrium phase diagrams are discussed. The phase structure of electrodeposited IB-Sn alloys conforms to the following empirical rules: terminal or intermediate substitutional solid solutions with close-packed structure are obtained over a composition range close to the maximum solubility range observed in equilibrium phase diagrams; phases with long range order are not obtained by electrodeposition; NiAs structure type phases are obtained over an enlarged composition range compared to that of their equivalent structure in the equilibrium diagrams. Peculiarities of phase formation in electrodeposited alloys are discussed with reference to phase stability calculations according to equilibrium thermodynamics, introducing free energy-composition diagrams modified in order to account for the absence of phases with long range order.