PHASE-SEPARATION IN AMORPHOUS ZR-CO AND ZR-FE ALLOYS

Amorphous Zr-Co and Zr-Fe alloys were prepared by melt spinning and co -sputtering and investigated by electromotive force measurements. The experiments show constant chemical potentials in different concentrati on ranges, which are indicative of the presence of two amorphous phase s in both alloy systems. The thermodynamic data are analysed using the calculation-of-phase-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 fro m 37 to 62 at.% Fe. The calculation of the enthalpies of mixing and th e Gibbs energies shows that, in both systems, one amorphous phase has its maximum stability at about equiatomic composition, whereas a secon d minimum of the Gibbs energy is located at Zr-poor concentrations. Th e different two-phase range of amorphous Zr-Co compared with that of Z r-Fe is explained by the relative stabilities of the chemical order in the amorphous phases, which differ in these alloy systems.