Thermodynamic properties of Pd-based glass-forming alloys

Undercooled liquids of the easy glass-forming alloys Pd-Ni-P and Pd-Cu-Ni-P (Pd40Ni40P20, Pd40Ni10Cu30P20, Pd43Ni10Cu27P20) have an extra-ordinary stability against crystallization allowing for direct calorimetric measurements of this metastable state. The liquid alloys can be undercooled consistently into the glassy state at moderate cooling rates of about 0.2 K/s and heat capacity measurements have been performed covering the undercooling regime from the melting temperature to the glass transition temperature. The thermodynamic functions of the alloys in dependence on temperature were evaluated. The isentropic temperature, T-K, Often interpreted as the low temperature limit of the liquid state, was determined from the excess entropy. Enthalpy relaxation experiments show that the addition of Cu leads to an increase in the fragility of the Pd-based alloys. (C) 1999 Elsevier Science B.V. All rights reserved.