Фазовая диаграмма системы Cu-Rh

К оглавлению: Другие диаграммы (Others phase diargams)


Cu-Rh (Copper-Rhodium) D.J. Chakrabarti and D.E. Laughlin The equilibrium phases in the Cu-Rh system are (1) the liquid; and (2) the fcc phase that forms a continuous solid solution between Cu and Rh at high temperature, and decomposes at lower temperatures into two fcc solid solution phases, one rich in Cu and the other rich in Rh. The assessed phase diagram of the Cu-Rh system is derived primarily from the work of [71Rau], based on microstructural and X-ray investigations. Because no thermal analysis measurements were made, the liquidus was not determined. The Cu-Rh system is characterized by the presence of an isomorphous solid across the entire diagram in the temperature regions immediately below the solidus. The solidus determined by the incipient fusion technique appears nearly flat between approximately 25 and 50 at.% Rh. This would imply a shallow free-energy versus composition curve of the solid in corresponding composition and temperature ranges and a tendency toward formation of a miscibility gap at lower temperatures. A single-phase continuous solid solution field exists between the components below the solidus. At still lower temperatures, the phase field enters into a wide miscibility gap wherein it separates into two equilibrium isostructural phases, one of which is rich in Cu and the other in Rh. The critical temperature and composition of the gap are 1150 C and 60 at.% Rh, according to [71Rau]. The miscibility gap boundary given by [71Rau] has been modified slightly in this evaluation in order to include, inside the gap, the compositions for which the X-ray showed a two-phase structure. The gap boundaries at 800 C, according to [71Rau], are approximately at 25 and 90 at.% Rh. The existence of a metastable single-phase continuous solid solution between ( Cu) and (Rh) was established by [64Luo], based on rapid solidification of the alloys from the melt. This is in agreement with the generally accepted conditions for mutual solubility of metals in the solid state, which Cu and Rh satisfy. Transition to equilibrium phases occurred when the samples were heated at 600 C for seven to ten days. 64Luo: H.L. Luo and P. Duwez, J. Less-Common Met., 6,248-249 (1964). 71Rau: Ch.J. Raub, E. R”schel, D. Menzel, and M. Gadhof, Metall, 25(7), 761- 762 (1971). Published in Bull. Alloy Phase Diagrams, 2(4), Mar 1982. Complete evaluation contains 1 figure, 2 tables, and 10 references. 1