Фазовая диаграмма системы Cu-Ir

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Cu-Ir (Copper-Iridium) D.J. Chakrabarti and D.E. Laughlin The characteristics of the Cu-Ir phase diagram are reasonably well established, although the system has only been studied in part. Limited terminal solid solubility fields occur with both Cu and Ir, and the (Ir) solidus exhibits retrograde behavior above the peritectic temperature. The equilibrium phases of the Cu-Ir system are (1) the liquid, L, miscible in all proportions and stable down to the melting point of Cu at 1084.87 C; (2) the fcc solid solution, (Cu), which has a maximum solubility of ~8 at.% Ir at 1138 с 5 C; and (3) the fcc solid solution, (Ir), which has a maximum solubility of 6.3 at.% Cu at 1850 C. The assessed phase diagram is based on the work of [69Rau] below 1200 C. The higher temperature portion of the diagram (above 1138 C) was estimated from calculations based on thermodynamic modeling of the experimental phase diagram data. The present diagram shows a slight discrepancy between the calculated and the experimental solidus for the (Ir) phase above 1300 C. The experimental results, especially at higher solute ranges, may not be very reliable. The calculated liquidus shows an inflection point, which indicates the likelihood that the liquid develops a metastable miscibility gap at lower temperatures. This was confirmed by thermodynamic modeling that gave a critical temperature of about 350 C. In the solid state, Cu and Ir have restricted mutual solubility, which is quite unlike the behavior of Cu with Rh, in the same group as Ir, or with the neighboring Pt and Pd. All of these elements exhibit complete miscibility in the solid. Thermodynamically, the Cu-Ir system is not very different from the Cu-Rh system, in that the clustering effect predominates in both systems with decreasing temperatures. The critical point of the metastable miscibility gap between the two fcc terminal solid solution phases in the Cu-Ir system extends above the solidus. Thus, the intersection of the miscibility gap with the solidus gives rise to a peritectic-type diagram in the Cu-Ir system. The peritectic invariant temperature is 1138 с 5 C, and the corresponding reported compositions of the liquid, (Cu), and (Ir) phases are ~4, ~8, ~97 at.% Ir, respectively. 69Rau: E. Raub and E. Roeschel, Z. Metallkd., 60, 142-144 (1969) in German. Published in Bull. Alloy Phase Diagrams, 8(2), Apr 1987. Complete evaluation contains 2 figures, 3 tables, and 9 references. 1