Thermodynamics and fragility of glass-forming alloys

The existing correlation between the extensive properties, DH and DS, the enthalpy and entropy difference between liquid and crystal phases has been checked to relate metallic glasses to other classes of amorphous materials. Expressing the specific heat difference, DCp, of molten and crystalline metallic glass-formers as a function of temperature with different functional trends, parametric expressions of fragility are derived using relevant temperatures for alloys. It is shown that relationships between the DSg/DCp,g ratio and such temperatures are useful to estimate unknown quantities when the experimental determination of the specific heat is possible. Thermodynamic indicators of fragility are compared to the kinetic fragility obtained from viscosity data accounting for the estimated errors on parameters which are derived from extrapolations. The outcome of the analysis indicates that a relationship between thermodynamic and kinetic parameters exists. Moreover a systematic scatter for some alloys indicates a diverse behavior which can be ascribed to structure modification either in the liquid or in the solid reference state.