COST 507 - Repositório Aberto da Universidade do Porto

An Experimental Investigation of the Cu-Mg-Zr
Phase Diagram
Nataliya Bochvar*, Marko Hämäläinen**,
Lazar Rokhlin*, Evgeniya Lysova*
*Baikov Institute of Metallurgy Academy of Science of Russia,
Moscow, Russia
"Helsinki University of Technology, Institute of Materials
Science and Technology, Espoo, Finland
Abstract
This research forms part of COST 507 project "Thermodynamic assessment of the
system Cu-Al-Mg-Zr-Li". The work included the experimental investigation of
Cu-Mg-Zr phase diagram as the subsystems of general system Cu-Al-Mg-Zr-Li. A
number of the alloys of Cu-Mg-Zr system were prepared by melting. The
differential thermal analysis of the alloys was conducted and the structure of them
were studied by different methods. The results of the experiments enabled to
construct isothermal and polythermal sections of the phase diagram. The
experimental investigations carried out in Baikov Institute of Metallurgy and the
optimization of theses data with use by the thermodymic calculations carried out
in Helsinki University of Technology.
1 Introduction
The experimental data on Cu-Mg-Zr system are very limited. [82Kuz] constructed
the polythtemal section in Cu-corner for constant Mg concentration 1 at.% and
from 0 up to 15 at.% Zr using differential thermal analysis, X-ray phase analysis
and microscopic method. No ternary compounds have been found in the alloys.
The phases CugZ^ and Cu?Zr2 ( or CusiZr^) of the Cu-Zr system are existed.
[59Ish, 68Bab] studied the solubility of Zr in molten Mg at 700 °C with copper
additions up to about 0.4 at.% Cu [59Ich] and at 780-800 °C with copper
additions up to 0.6 at.% Cu [68Bab]. According X-ray investigations [59Ich] (Zr),
Mg2Cu and CuZr2 are in equilibrium with Mg phase. This work was undertaken
to enlarge the knowledge about the Cu-Mg-Zr phase diagram in the Cu corner up
to 40 wt.% (64 at.%) Mg and 40 wt.% (32 at.%) Zr.
2 Experimental Procedure
Cu-Mg-Zr alloys (120 compositions) were prepared by arc melting under He
atmosphere (for alloys with up to 10 wt.% Mg) and by induction melting under
Ar atmosphere (for alloys with 10-50 wt.% Mg). The starting materials were Cu of
99.996 wt.%, Mg of 99.96 wt.%, and Zr of 99.9 wt.% purity. The alloys were
rolled for the height reduction of 50%, annealed at 500 °C for 100 h and then
quenched into cold water. The alloys were studied by microstructure analysis,
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