Viscosity of bulk and ribbon Zr-based glasses well below and in the vicinity of Tg:: A comparative study -: art. no. 132203

Tensile creep tests of bulk and ribbon samples of Zr52.5Ti5Cu17.9Ni14.6Al10 metallic glass have been performed over a wide range of heating rates. It has been found that a change of the quenching rate at least by three orders of magnitude exerts little influence on the shear viscosity below the glass transition temperature T-g. In all cases, the viscosity is strongly dependent on the heating rate, which can be explained as a result of irreversible structural relaxation with distributed activation energies. It is argued that the volume spectral density of relaxation centers in the high-energy part of the activation energy spectrum (AES) of irreversible structural relaxation is higher for ribbon samples than that for bulk specimens by about 30%, whereas the low-energy part of the AES remains unchanged. Above T-g, the viscosity of bulk samples is always lower than that of ribbons, which may be interpreted in terms of the phase decomposition.