Фазовая диаграмма системы Tc-W

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Tc-W (Technetium-Tungsten) S.V. Nagender Naidu and P. Rama Rao The Tc-W system consists of an intermediate s phase [61Dar, 63Nie] and terminal solid solutions of (Tc) and (W) [63Nie]. The assessed phase diagram is speculative, suggesting that the s phase is formed by a peritectic reaction occurring at about 1900 C and that the system has a eutectic reaction at about 1800 C and 37 at.% W. The diagram is based on the analogous Tc-Mo phase diagram [Molybdenum]. The primary difference between the Tc-Mo diagram and the proposed Tc-W phase diagram is the existence of a Cr3Si-type phase in the Tc-Mo system, which is not found in the Tc-W system. It must be emphasized that the liquidus and solidus of the proposed Tc-W diagram should be considered only as a guide until experimental studies become available. The solid solubility of Tc in (W) is 55 at.% Tc at 1800 C; that of W in (Tc) is 12 at.% W at the same temperature. The mutual solubilities decrease as temperatures decrease. The homogeneity range of the s phase, which extends from 25 to 28 at.% W at 1800 C, widens as temperatures decrease; however, the mode of its formation is not known. 61Dar: J.B. Darby, Jr. and D.J. Lam, Report ANL-6516, U.S. At. Energy Commission, Argonne National Laboratory, Argonne, IL, 254-256 (1961). 62Dar: J.B. Darby, Jr., D.J. Lam, L.J. Norton, and J.W. Downey, J. Less-Common Met., 4, 558-563 (1962). 63Nie: J. Niemiec, Bull. Acad. Pol. Sci. Ser. Sci. Chim., 11, 311-316 (1963). To be published in Phase Diagrams of Binary Tungsten Alloys, 1991. Complete evaluation contains 1 figure, 2 tables, and 8 references. 1