Viscous behaviour of undercooled metallic melts

Viscosity data for non-crystalline Au_0.77Ge_0.136Si_0.094 alloys in the region of the glass transition temperature and above the melting point, are fitted to a single expression of the type proposed by Doolittle. This expression also leads to reasonable values for the activation energy for hole formation in the liquid and for the liquid free volume at the glass transition temperature. A similar procedure was applied to the viscosity data of a Pd_0.775Cu_0.06Si_0.165 non-crystalline alloy. By assuming values for the liquid free volume at both the glass transition temperature and the melting point, the analysis is also extended to Pd_0.82Si_0.18 alloys for which no viscosity data are available. Here, time-temperature-transformation (T-T-T) curves for crystallization are calculated for each of the three alloys, and used to determine the critical cooling rates for the formation of an amorphous solid.