Abstract
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. Die Bildungsenthalpien der intermetallischen Verbindungen Zr2Cu, ZrCu und der amorphen Legierung Zr0,55Cu0,45 werden mit einem Losungskalorimeter auf der Basis von flussigem Aluminium gemessen. Die Kristallisationsenthalpien der amorphen Legierungen Zr1 —xCux mit x = 0,38; 0,45; und 0,55 werden mit einem Differential-Abtast-Kalorimeter bestimmt. Es wird gefunden, das alle Werte relativ klein sind im Vergleich zu Aktivierungsenergien aus einer Untersuchung der Kristallisationstemperatur in Abhangigkeit von der Aufheizgeschwindigkeit. Der Enthalpieunterschied zwischen amorphen und kristallinen Materialien wird mit dem Modell von Miedema analysiert. Die Ergebnisse zeigen, das die niedrigere Enthalpie des ersteren Materials hauptsachlich durch eine weniger effektive Umgebung der Atome durch unahnliche Atome verursacht wird.
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