The initial part of this investigation was to
determine the ternary isothermal sections for the
Cr-Co-Cu system and the Cr—Mm-Cu system at lOOO°C.
and 975°C., respectively. This was done by vacuum
melting the Cr-Co~Cu alloys and annealing these alloys
in an inert atmosphere of a helium-hydrogen gas mixture.
The Cr-Mn-Cu alloys were melted under a helium
atmosphere and annealed in evacuated Vycor tubes. By
the use of metallographic techniques and x-ray analysis
the phases present in each alloy were determined and
the two ternary isotherml sections constructed.
It was found that copper had a very limited solid
solubility in the sigm phase of both systems. The
sigma field in the Cr-Co—Cu l0O0°C. ternary isothermal
comes into equilibrium with the terminal solid solutions
of chromium, cobalt, and copper. In the Cr-Mn-Cu
ternary isothermal section sigma comes into equilibrium
with the terminal solid solution of chromium and cobalt
and the face-centered cubic solid solution of copper
in manganese. From these data the electron vacancy
scheme(16) may not be extended to include copper due to the limited solid solubility of copper in sigma.
Also, the extent of copper solubility in the sigmas
cannot be related to the solubility of the oopper in
cobalt or manganese.
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