Tensile creep tests of bulk and ribbon samples of Zr 52.5 Ti 5 Cu 17.9 Ni 14.6 Al 10 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 ͑AES͒ 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.

The article presents the results of nonisothermal creep measurements of the Zr52.5Ti5Cu17.9Ni14.6Al10 bulk metallic glass in a wide range of heating rates well below and in the vicinity of the glass transition temperature Tg. It is shown that the shear viscosity η is strongly dependent on the heating rate Ṫ:η increases linearly with Ṫ−1 at T<Tg, while an increase of η with Ṫ is observed at T>Tg. It is argued that the heating rate dependence of the shear viscosity below the glass transition region is controlled by irreversible structural relaxation and can be quantitatively described by the directional structural relaxation model. A possible reason for the η(Ṫ) dependence in the glass transition region is discussed.

No abstract