Shear viscosity of bulk and ribbon glassy Pd40Cu30Ni10P20 well below and near the glass transition

Abstract

Measurements of the shear viscosity η of bulk and ribbon glassy Pd40Cu30Ni10P20 in a wide range of temperatures and heating rates Ṫ have been performed. It has been determined that η is strongly dependent on Ṫ below the glass transition temperature Tg, in agreement with earlier viscosity data on other metallic glasses, and independent of Ṫ above Tg, in contrast to previously reported data for Zr-based bulk and ribbon glasses. The heating rate dependencies of the glass transition temperature and shear viscosity at T=Tg have been studied in detail. It has been found that the inverse glass transition temperature logarithmically decreases with the heating rate while the shear viscosity at the glass transition upon glass production is by several orders of magnitude smaller than 1012Pa×s usually assumed for this case. The viscosities of bulk and ribbon samples below Tg are nearly the same, in spite of four-orders-of-magnitude difference in the production quenching rates, whereas the density is notably smaller for the ribbons. Those latter facts are shown to be in evident disagreement with the free volume model.