THERMODYNAMICS OF UNDERCOOLED LIQUIDS AND ITS APPLICATION TO AMORPHOUS PHASE-FORMATION

The thermodynamic functions of undercooled liquids and amorphous phases can be determined most favourably by utilizing the CALPHAD method. Therefore, calorimetric and e.m.f. investigations have been employed on amorphous phases. The results demonstrate the metastable state of the amorphous alloys, and show that the thermodynamic functions of the undercooled liquid are strongly influenced by an excess specific heat, which stabilizes the undercooled liquid at low temperatures. The excess specific heat reflects the chemical and topological ordering of the liquid on cooling, which can result in the occurrence of an inverse melting point and in phase separation in the amorphous state. In addition, e.m.f. measurements confirm the validity of the Gibbs-Duhem equation. Thus phase diagrams of metastable phases can be calculated for undercooled liquids and amorphous phases which can be used to determine the concentration ranges for amorphous phase formation by various preparation methods.