Alloy phases formed in immiscible Cu-Mo and Cu-W systems by multilayer-technique

By adding an estimated interfacial free energy contribution, Cu-Mo and Cu-W multilayered films were properly designed to possess an abnormally high free energy. For the Cu-Mo system, room temperature 200 keV xenon ion mixing of the multilayers resulted in the formation of Mo-enriched amorphous alloys and some Cu-based metastable fee solid solutions. While for the Cu-W system, thermal annealing of the multilayers resulted in the formation of some metastable alloys. To elucidate this unusual alloying behavior, free energy curves of the respective phases and of the multilayered films were calculated based on Miedema's model. It turned out that the interfacial free energy in the multilayered films elevated the initial energy level of the multilayers to a state higher than that of the observed metastable phases and therefore served as a driving force for alloying in these immiscible systems. (C) 1997 Elsevier Science S.A.