Фазовая диаграмма системы Cr-Pb

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Cr-Pb (Chromium-Lead) M. Venkatraman and J.P. Neumann No comprehensive investigations of the binary Cr-Pb system were found in the literature. However, the assessed (tentative) Cr-Pb phase diagram is based on the exploratory thermal analysis and metallographic studies of [08Hin] and the solubility measurements of Cr in liquid Pb of [58Ald]. The diagram is characterized by the absence of intermediate phases and by extensive immiscibility in the liquid state and essential immiscibility in the solid state. According to the limited data of [08Hin], the liquid miscibility gap extends at the monotectic temperature of ~1470 C from ~9 to at least 43 at.% Pb. No determinations of the boundaries of the liquid miscibility gap were carried out at higher temperatures because of the high vapor pressure of Pb--1 bar at 1751 C for pure Pb [Hultgren,E]. Because the adopted melting temperature of Cr is about 300 C higher than the melting temperature of the Cr used by [ 08Hin], it is possible that the true monotectic temperature is actually higher than is shown in the assessed diagram. The low melting temperature of Cr reported by [08Hin] was probably due to the low purity of the Cr used (~98.5 wt.%) and to contamination by carbon and nitrogen during the experiments. The solubility of solid Cr in liquid Pb at the monotectic L1 = (Cr) + L2 and at the three-phase equilibrium L + (Cr) + (Pb) can be estimated by extrapolating the solubility data of [58Ald] to the corresponding temperatures of ~1743 K (1470 C) and ~600 K (327 C), respectively. At the monotectic, the solubility value ~3 at.% Cr is obtained; at the melting temperature of Pb, the solubility is calculated to be ~1 x 10-7 at.% Cr. The value of 3 at.% Cr is adopted for the miscibility gap in the assessed diagram. 08Hin: G. Hindrichs, Z. Anorg. Chem., 59, 414-449 (1908) in German. 58Ald: T. Alden, D.A. Stevenson, and J. Wulff, Trans. Metall. Soc. AIME, 212, 15-17 (1958). Published in Bull. Alloy Phase Diagrams, 9(2), Apr 1988. Complete evaluation includes 2 figures, 2 tables, and 5 references. Special Points of the Cr-Pb System