Amorphous alloys formed by ion mixing or solid-state reaction in immiscible Y-refractory metal systems and their elastic properties

This paper presents the formation of amorphous alloys in the Y-refractory metal systems, which have a rather positive heat of formation, by ion mixing or solid-state reaction of multilayers and the elastic properties of the amorphous alloys. An estimation showed that the excess interfacial free energy stored in the multilayered films elevated the initial energetic state of the films to a level higher than that of the amorphous phase in a certain range, thus providing a driving force for alloying. Accordingly, the multilayers were designed to include enough fraction of interfacial atoms versus the total atoms, and amorphous alloys were indeed obtained by either room-temperature 200-keV xenon-ion mixing or solid-state reaction. Moreover, the elastic modulus and hardness changes were characterized by nanoindentation for the formed amorphous films. The change of elastic property upon thermal annealing also served as an evidence in support to the free volume model proposed for the amorphous structure.