Фазовая диаграмма системы Au-K

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Au-K (Gold-Potassium) A.D. Pelton The assessed phase diagram for the Au-K system is based almost entirely on the work of [61Kie], although some phase boundaries, particularly those shown as dashed lines, are different from their work. The existence of four compounds is reasonably well established, although their ranges of homogeneity are not known. According to [61Kie], Au2K and AuK2 melt incongruently. AuK most probably melts incongruently. Although Au5K is shown in the present diagram to melt congruently, this is only speculative, as is the form of the liquidus for K concentrations below 30 at.%. Error limits of с25 to с50 C should be placed on the entire liquidus in the assessed phase diagram. Boundaries shown by dashed lines represent the largest uncertainty. The assessed peritectic and eutectic temperatures are probably accurate to с5 C, except for the eutectic at 57 C, which is probably correct to с3 C. However, recent unpublished emf studies [84Ega] conducted at 750 C show serious disagreement with the assessed diagram. The compound Au2K was found to exist at 750 C. The liquidus at 750 C was found at a much higher K concentration than the assessed value. Pending verification, the assessed diagram should be used with caution. The solubility of Au in (K), measured between 6 and 53 C [70Smi], is given by: at.% Au = (2.2 -2+6 ) C 103 exp (-3926 с 400/T), where T is in kelvin. The solubility of K in (Au) is expected, on the basis of atomic size parameters, to be very small. 61Kie: G. Kienast and J. Verma, Z. Anorg. Allg. Chem., 310, 143-169 (1961) in German. 70Smi: F.A. Smith and L.W. Barr, Philos. Mag., 21, 633-637 (1970). 84Ega: J. Egan and R. Algasmi, Brookhaven National Laboratory, private communication (1984). Published in Phase Diagrams of Binary Gold Alloys, 1987, and Bull. Alloy Phase Diagrams, 7(1), Feb 1986. Complete evaluation contains 1 figure, 1 table, and 12 references. 1