Фазовая диаграмма системы Ti-W

К оглавлению: Другие диаграммы (Others phase diargams)

Ti-W (Titanium-Tungsten) J.L. Murray This assessment differs significantly from [Hansen], [Elliott], and [Shunk]. The evaluation by [Hansen] relied on the diagram proposed by [53May], in which a bcc miscibility gap is shown persisting up to a peritectic reaction L + (W) = (bTi) at 1800 C. However, by metallographic and X-ray studies, [68Rud] showed that a complete range of (bTi,W) solutions exists above a critical point at about 1250 C and that there is no peritectic reaction. Experimental studies of the liquidus and solidus have been made by [53May], [ 54Now], [68Rud], and [71Ole]. High-temperature data of [53May] are not used in the present assessment. In the range 0 to 10 at.% W, however, the work of [ 53May] is consistent with the other determinations. The assessed phase boundaries represent the results of optimizations of Gibbs energies with respect to the data of [54Now], [68Rud], and [71Ole]. The monotectoid reaction (bTi) = (aTi) + (W) is sluggish, and the discrepancy between thermal analysis arrests on heating [71Ole] and metallographic studies [53May] is 45 C. The monotectoid reaction is placed at 740 с 20 C, somewhat below the heating arrests [71Ole], but above the values based on microscopic studies. The assessed (bTi) transus is based on [61Img]. Bcc (bTi,W) cannot be retained during quenching in alloys containing less than about 6 at.% W [53Duw, 53May, 71Ole]. For alloys containing 0 to 2 at.% W, the cph structure (a›) is formed martensitically; for alloys containing 2 to 6 at.% W, the martensite has an orthorhombic structure that is a distortion of the cph lattice [71Mor]. w formation in the Ti-W system has been reported by [73Ika] and others. w forms during either quenching (athermally) or annealing in the approximate range 30 to 450 C. 53Duw: P. Duwez, Trans. ASM, 45, 934-940 (1953). 53May: D.J. Maykuth, H.R. Ogden, and R.I. Jaffee, Trans. AIME, 197, 231-237 ( 1953). 54Now: H. Nowotny, E. Parthe, R. Kiefer, and F. Benesovsky, Z. Metallkd., 45(3) , 97-99 (1954) in German. 61Img: A.G. Imgram, D.N. Williams, R.A. Wood, H.R. Ogden, and R.I. Jaffee, WADC Tech. Rep. 59-595, Part II (1961). 68Rud: E. Rudy and St. Windisch, Trans. AIME, 242, 953-954 (1968). 71Mor: H.A. Moreen, Metall. Trans., 2, 2953 (1971). 71Ole: S.V. Oleynikova, T.T. Nartova, and I.I. Kornilov, Izv. Akad. Nauk SSSR, Met., (3), 192-196 (1971) in Russian; TR: Russ. Metall., (3), 130-133 (1971). 73Ika: H. Ikawa, S. Shin, M. Miyagi, and M. Morikawa, Sci. Technol. Appl. Titanium, Proc. Int. Conf., R.I. Jaffe, Ed., 1545-1556 (1973). Published in Phase Diagrams of Binary Titanium Alloys, 1987, and Bull. Alloy Phase Diagrams, 2(2), Sep 1981. Complete evaluation contains 3 figures, 6 tables, and 18 references. Special Points of the Ti-W System