Фазовая диаграмма системы Fe-H

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Fe-H (Iron-Hydrogen) A. San-Martin and F.D. Manchester The phase diagram for the Fe-H system at atmospheric pressure consists of (1) a and (2) d, two solid solutions of H based on the low- and high-temperature bcc forms of pure Fe; (3) g, the solid solution of H based on the fcc form of pure Fe; and (4) the liquid, L. In metal-hydrogen systems, the equilibrium pressure of the H surrounding the metal is always a significant thermodynamic variable, in contrast to most situations involving metallic alloys. The phase boundaries in the assessed diagram have been calculated and are based on review of the experimental data [69Gon, 70Ori, 76Bun, 76Sil1, 76Sil2, 78Vol, 79Pre, 80Ant, 80Hir, 83Kiu]. They represent the maximum assessed H solubility in solid and liquid Fe at P = 0.1 MPa and do not necessarily demarcate the range of existence of equilibrium phases. The dissolved quantities of H are small; the atomic ratio X (X = H/Fe) ranges from 7 x 10-4 just below the melting temperature of Fe and to less than 3 x 10-8 at room temperature. Therefore, the effects of H on the temperatures of the three-phase equilibria should also be small and difficult to measure. The lowering of the melting point of Fe by 1.8 C proposed by [50Gel] and corroborated experimentally by [77Bun] has been incorporated into the assessed diagram. At hydrogen pressures higher than the normal (normal conditions imply atmospheric pressure and room temperature), the H solubility in Fe increases, and the position of the critical points is displaced [76Bun]. From an investigation extending up to hydrogen pressures of 100 MPa, [77Sha1] concluded that the major changes occur at pressures of up to 25 to 30 MPa and that further increases in pressure do not introduce noticeable changes. At 40 MPa pressure, the dissolved H appreciably reduces the melting point of Fe and broadens the existence range of gFe [76Bun1, 77Sha2]. The temperatures for the corresponding three-phase equilibria at 40 MPa are 1508 C for L = d + H2 (eutectic-type or gas eutectic [77Sha1]), 1408 C for d + H2 = g (peritectoid-type or gas peritectoid [81Sha]), and 894 C for g = a + H2 (eutectoid-type or gas eutectoid [81Sha]). [77Sha1] estimated that the boundaries of the gas eutectic and the gas peritectic equilibria will come close together and finally merge in a four-phase equilibrium line at around 42. 5 MPa and 1495 C. Under normal conditions, the solubility of H in pure solid Fe is very small and increases only at hydrogen pressures in the GPa range, where the formation of a new phase has been reported. [80Ant] reported on the formation of e phase by holding Fe samples 10 h in hydrogen at pressures of 6.7 GPa at 250 C. The transformation of the original Fe sample into e phase was only partial, and it was successfully preserved at atmospheric pressure by quenching down to -180 C. At atmospheric pressure, the composition of the cph phase varied between 0. 65 and 0.81 с0.03 and decomposed to hydrogen and bcc aFe at -120 C [80Ant]. The e phase is ferromagnetic with a Curie point TC above 80 K and a value of spontaneous magnetization (at atmospheric pressure and T = 0 K) similar to that for pure aFe [81Ant]. [38Sie] reported that the hysteresis effects associated with the g = d transformation [32Luc] are variable and are controlled by diffusion kinetics. Transforming to g phase, the solubility increases and values in this phase are higher than in a phase. The a = g transition is also marked by a solubility increase and exhibit a hysteresis similar to that of the g = d transition [ 38Sie]. [76Sil2] found that in the temperature range from the a <259> g transformation down to around 300 C the purity of aFe and the presence of grain boundaries do not have a significant effect on solubility. 32Luc: L. Luckemeyer-Haase and H. Schenck, Arch. EisenhЃttenwes., 6, 209 (1932) in German. 38Sie: A. Sieverts and H. Moritz, Z. Phys. Chem. (Leipzig), A183, 19-37 (1938) in German. 50Gel: W. Geller and Tak-Ho Sun, Arch. EisenhЃttenwes., 21, 423-430 (1950) in German. 69Gon: O.D. Gonzalez, Trans. Metall. Soc. AIME, 245, 607-612 (1969). 70Ori: R.A. Oriani, Acta Metall., 18, 147-157 (1970). 76Bun: K.P. Bunin, V.I. Shapovalov, and V.V. Trofimenko, Dop. Akad. Nauk Ukr. RSR, Ser. Fiz. Mat. Tech. Nauk, (3), 265-267 (1976) in Ukrainian. 76Sil1: J.R.G. da Silva, S.W. Stafford, and R.B. McLellan, J. Less-Common Met., 49, 407-420 (1976). 76Sil2: J.R.G. da Silva and R.B. McLellan, J. Less-Common Met., 50, 1-5 (1976). 77Bun: K.P. Bunin, V.I. Shapovalov, and V.V. Trofimenko, Zh. Fiz. Khim., 51, 1967-1970 (1977) in Russian; TR: Russ. J. Phys. Chem., 51(8), 1151-1153 (1977). 77Sha1: V.I. Shapovalov, L.M. Poltoratskii, and V.V. Trofimenko, Izv. V.U.Z. Chernaya Metall., (10), 100-102 (1977) in Russian; TR: Steel USSR, 7 (10), 586- 588 (1977). 77Sha2: V.I. Shapovalov and V.V. Trofimenko, Izv. Akad. Nauk SSSR, Met., (3), 125-129 (1977) in Russian; TR: Russ. Metall.; (3), 106-109 (1977). 78Vol: J. Volkl and G. Alefeld, in Hydrogen in Metals, Vol. 28, G. Alefeld and J. Volkl, Ed., Springer-Verlag, Berlin, Heidelberg, 321-348 (1978). 79Pre: G.M. Pressouyre, Metall. Trans. A, 10, 1571-1573 (1979). 80Ant: V.E. Antonov, I.T. Belash, V.F. Degtyarevo, E.G. Ponyatovskii, and V.I. Shiryaev, Dokl. Akad. Nauk SSSR, 252(6), 1384-1387 (1980) in Russian. 80Hir: J.P. Hirth, Metall. Trans. A, 11, 861-890 (1980). 81Ant: V.E. Antonov, I.T. Belash, E.G. Ponyatovskii, V.G. Thiessen, and V.I. Shiryaev, Phys. Status Solidi (a), 65, K43-K48 (1981). 81Sha: V.I. Shapovalov, L.M. Poltoratskii, V.V. Trofimenko, and N.P. Serdyuk, Fazovye Ravnovesiya Metallov y Splavakh, M.E. Drits, Ed., Izd. Nauka, Moscow, 280-285 (1981) in Russian. 83Kiu: K. Kiuchi and R.B. McLellan, Acta Metall., 31(7), 961-984 (1983). 86Wor: R. Wordel, F.E. Wagner, V.E. Antonov, E.G. Ponyatovskii, A. Permogorov, A. Plachinda, and E.F. Makarov, Hyp. Int., 28, 1005-1008 (1986). 87Min: C. Minot and C. Demangeat, J. Less-Common Met., 130, 285-291 (1987). Published in Bull Alloy Phase Diagrams, 11(2), Apr 1990. Complete evaluation contains 7 figures, 4 tables, and 91 references. 1