Phase separation in amorphous Zr-Co and Zr-Fe alloys

Abstract

Amorphous Zr-Co and Zr-Fe alloys were prepared by melt spinning and co-puttering and investigated by electromotive force measurements. The experiments show constant chemical potentials in different concentration ranges, which are indicative of the presence of two amorphous phases in both alloy systems. The thermodynamic data are analysed using the calculation-ofphase-diagrams method. In amorphous Zr-Co a two-phase region is found for compositions with between 63 and 77 at.% Co. In Zr-Fe the metastable equilibrium between two amorphous phases extends from 37 to 62 at.% Fe. The calculation of the enthalpies of mixing and the Gibbs energies shows that, in both systems, one amorphous phase has its maximum stability at about equiatomic composition, whereas a second minimum of the Gibbs energy is located at Zrpoor concentrations. The different two-phase range of amorphous Zr-Co compared with that of Zr-Fe is explained by the relative stabilities of the chemical order in the amorphous phases, which differ in these alloy systems.