Thermodynamic evaluation of phase equilibria in the ternary Cu–Cr–Ni system

The phase diagram in the ternary Cu–Cr–Ni system was calculated by a Calphad method. The molar Gibbs energy was expressed by a sub-regular solution model for the face-centered cubic (fcc) phase, the body-centered cubic (bcc) phase and the liquid (L) phase. The ternary interaction parameters of the fcc phase were evaluated on the basis of the observation in a previous study for phase equilibria in the ternary Cu–Cr–Ni system. The observation indicates that the miscibility gap exists at temperatures of T = 1073 and 1273 K for the fcc phase in the ternary Cu–Cr–Ni system, though the complete solid-solution phase is stable at T = 628–1358 K for that in the binary Cu–Ni system. As a result, the three-phase region of the fcc Cu-rich (α1), fcc Ni-rich (α2) and bcc Cr-rich (β) phases appears at T = 1073 and 1273 K. The observation is satisfactorily reproduced by the calculation. According to the calculation, the invariant reaction L + α → L + α1 + α2 occurs at T = 1487 K and that L + α2 → α1 + β takes place at T = 1402 K.