COST 507 - Repositório Aberto da Universidade do Porto

EXPERIMENTAL INVESTIGATION OF THE CU­MG­ZR SYSTEM.
Baikov Institute of Metallurgy, Moscow, Russia
Helsinki University of Technology, Espoo, Finland
Cu­Mg­Zr alloys (50 alloys) were prepared by arc melting under
He atmosphere (for alloys with up 10 wt.x Mg) and by induction
melting under Ar atmosphere (for alloys with 10­50 wt.ss Mg). The
alloys were rolled by the height reduction of 50X, annealed at
500°C for 100 h, quenched and studied by microcopy analysis, DTA,
microhardness measurements, X­ray analysis and microprobe X­ray
spectral analysis.
Data of the microprobe X­ray spectral analysis showed that:
­ there is a ternary compound called τ with composition of
54wt.3SCu, 10wt.X Mg, 36wtX Zr (50at.S Cu, ~25at.% Mg, ~25atX Zr)
and formulae ~Cu„MgZr; this compound is in equilibrium with
binary compounds Cu c ,Zr.., Cu„Mg and CuMg„ (see tabl.1, Fig.1);
01 14 ¿. á
- the binary compounds Cu c Zr and Cu CH Zr H . dissolve up to 1wt.%
O O1 14
(3at.X) Mg.
­ the binary compound Cu„Mg dissolve up to 4 wt.SS (2.5at.X) Zr.
Data of the X­ray diffraction analysis (the diffraction
patterns are shown in Fig.2) confirm the presence of the
ternary compound. So, there are some unidentified peaks besides
those of CUg.Zr.. and Cu„Mg, and these peaks can not be
recognized as the peaks of the other possible in this system
binary compounds. Therefore, it is naturally to suppose that this
peaks belong to the unknown ternary compound τ.
The data of the microstructure analysis (see Fig.3­after
annealing at 500°C and Fi.g.5­after DTA) showed the phases formed
in the studied area of concentration. The phases differ according
to their shape and color. After etching of the metallographic
specimens with the 30X solution of (NH.)„S„0 o the phase Cu E Zr is
4 d £. o o
seen as the thin plates having blue color, and Cu„Mg has black
color. The phase CUg.Zr.. . forms crystals of regular shape and
white color. The phase τ rounds the CUg.Zr. crystals. It is of
grey or light brown color. The isothermal section at 500°C was
constructed (Fig.4).
DTA was carried out for all prepared alloys. One polythermal
section (between Cu­10wt.X Zr and Cu­7wt.x Mg) was constructed
(Fig.6), as we11.
213 ­