COST 507 - Repositório Aberto da Universidade do Porto

The Cu-Cr-Zr Phase Diagram and Its Applications
K .Zeng* and M. Hämäläinen**
institute of Materials Research, GKSS-Research Center, Germany
**Helsinki University of Technology, Espoo, Finland
Abstract
The phase diagrams of the Cu-Cr-Zr ternary and its sub-binary systems were
optimised and calculated by using the CALPHAD method. An experiment was also
carried out to check the reliability of the optimised thermodynamic parameters and
clear up the confusion concerning the phase relationships in the Cu-rich corner of the
Cu-Cr-Zr phase diagram. All the experimental data from the literature, phase diagram
data and thermodynamic data, were evaluated carefully before being used in
optimisation. The adjustable parameters of a thermodynamic model for each phase
were selected by considering what thermodynamic quantities are connected with the
measured values and how these quantities are connected with the parameters. When
the entropy term is necessary in the case where Gibbs energies or phase diagram data
are measured within a narrow temperature range, the Tanaka-Gokcen-Morita
relationship was used to keep the ratio of enthalpy of mixing to the excess entropy of
mixing constant.
A complete thermodynamic description of the Cu-Cr-Zr system was obtained and used
to calculate various phase diagram sections which are of theoretical and practical
importance. Some experimental results from the literature were discussed on the basis
of the calculated phase diagrams. The existence of the pseudobinary Cu-Cr 2 Zr system
proposed in the literature has been ruled out. The results of the present study can be
used not only as references for the experimental investigations on optimisation of the
composition of Cu-Cr-Zr alloys and their production techniques, but also be combined
with other evaluations based on the same type of thermodynamic models to provide a
thermodynamic basis for alloy design.
Publications
1. Kejun Zeng, Marko Hämäläinen, and Kaj Lilius, "Thermodynamic Modeling of
theLaves Phases in the Cr-Zr System", CALPHAD 1993, 17 (1), 101-107.
2. Kejun Zeng and Marko Hämäläinen, "A Thermodynamic Assessment of the Cr-
Zr System", Z. Metallkde. 1993, 84 (1), 23-28.
3. Kejun Zeng and Marko Hämäläinen, "Thermodynamic Analysis of Stable and
Metastable Equilibria in the Cu-Cr System", CALPHAD 1995, 19(1), 93-104.
4. Kejun Zeng, Marko Hämäläinen, and Hans Leo Lukas, "A New Thermodynamic
Description of the Cu-Zr System", J. Phase Equilibria 1994, 15 (6), 577-586.
- 228 -