Фазовая диаграмма системы Cr-Hf

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Cr-Hf (Chromium-Hafnium) M. Venkatraman and J.P. Neumann The Cr-Hf system has a single intermediate phase, Cr2Hf, two eutectic reactions, L = (Cr) + Cr2Hf and L= Cr2Hf + (bHf), and one eutectoid reaction, ( bHf) = Cr2Hf + (aHf). The assessed diagram is based on the work of [65Sve], [ 68Car], and [68Rud]. All temperatures have been adjusted to IPTS-68. Commercial Hf usually contains Zr as a major impurity. Because the melting point of Zr is about 400 C lower than that of Hf, the presence of Zr shifts the solid-liquid phase boundaries to lower temperatures, but this variation is within the experimental uncertainties [68Car, 68Rud]. The existence of the intermediate phase Cr2Hf is well established; its congruent melting temperature is 1825 с 20 C. At least two modifications of the intermediate phase Cr2Hf are known: a high-temperature hexagonal (MgZn2- type) form and a low-temperature cubic (MgCu2-type) form. Both modifications have a small homogeneity range, which extends approximately from 33 to 35 at.% Hf. The mutual solid solubilities of Cr and aHf are small; the solubility of Cr in (aHf) is ~1 at.% Cr at about 1400 C. The Cr-Hf system closely resembles the Cr-Zr diagram. 65Sve: V.N. Svechnikov, A.K. Shurin, and G.P. Dmitrieva, Fazovye Prevrashcheniya Metallakh Splavakh, Akad. Nauk Ukr. SSR, 159-162 (1965) in Russian. 68Car: O.N. Carlson and D.G. Alexander, J. Less-Common Met., 15, 361-370 (1968) . 68Rud: E. Rudy and S.F. Windisch, J. Less-Common Met., 15, 13-27 (1968). Published in Bull. Alloy Phase Diagrams, 7(6), Dec 1986. Complete evaluation contains 2 figures, 3 tables, and 11 references. 1