Thermodynamics and amorphization of the copper–zirconium alloys

Abstract

The vapour composition and the thermodynamic properties of Cu–Zr alloys in the liquid and solid states have been studied by Knudsen-cell mass spectrometry over the temperature (701–1823 K) and composition (5.1–97.3 mol% Zr) intervals. The accessible temperature range has been enhanced by chemically generating volatile substances directly in the cell. For this purpose, the samples have been mixed with powdered fluorides of magnesium, calcium, sodium or potassium. Reduction reactions occurring in the cell produced zirconium fluorides, which have been examined with the mass spectrometer. The thermodynamic functions of formation of all crystalline phases in the Cu–Zr system have been determined. A representative file of experimental data has been obtained for the Cu–Zr melt. It comprises about 1100 values of the activities of both components at various concentrations and temperatures. The concentration and temperature dependences of the thermodynamic functions of the Cu–Zr melt have been described using the associated-solution concept with allowance for CuZr and Cu2Zr association types. The phase equilibria computed on the basis of the obtained thermodynamic properties and the developed model are shown to agree with the available experimental data. The nature of the interparticle interaction in the Cu–Zr system has been analysed and the behaviour of the thermodynamic functions accompanying the process of transition of the Cu–Zr melt into the amorphous state was considered. Quantitative agreement with the independent experimental results was obtained.