Enthalpy Effects in Amorphous Alloys and Intermetallic Compounds in the System ZrCu

The enthalpies of formation are measured in the intermetallic compounds Zr2Cu, ZrCu and the amorphous alloy Zr0.55Cu0.45 by means of a solution calorimeter based on liquid aluminium. The crystallization enthalpies of the amorphous alloys Zr1 —xCux with x = 0.38, 0.45, and 0.55 are determined by means of a differential scanning calorimeter. All these values are found to be relatively small compared with the activation energies for crystallization derived from a study of the crystallization temperature as a function of the heating rate. The enthalpy difference between amorphous and crystalline materials is analysed in terms of Miedema's model. The results indicate that the lower enthalpy content in the former materials is mainly due to a less effective surrounding of the atoms by dissimilar atoms.