Thermodynamics of the Au49Ag5.5Pd2.3Cu26.9Si16.3 glass-forming alloy

The thermodynamic properties of Au49Ag5.5Pd2.3Cu26.9Si16.3, the best Au-based glass-former, were investigated using differential scanning calorimetry. The specific heats of the amorphous, undercooled liquid, and crystal phases and enthalpies of transformation were determined. The differences in enthalpy and entropy of the undercooled melt with respect to equilibrium crystalline phases were calculated. The thermodynamic fragility index (mT), introduced by Angell [1] in relation to the loss of entropy of the liquid phase on undercooling to the glass transition temperature, was derived and compared to fragility indexes of both metallic and conventional glass-formers; in particular with another gold alloy, Au77Ge13.6Si9.4. Furthermore it was correlated to the kinetic one obtained from dynamic measurements [2].