Фазовая диаграмма системы H-Ti

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H-Ti (Hydrogen-Titanium) A. San-Martin and F.D. Manchester The Ti-H system is of the eutectoid type and consists of the following phases: the cph a phase and the bcc b phase; two interstitial solid solutions of H based on the allotropic a and b forms of pure Ti; d, an fcc hydride; e, a tetragonally distorted fcc or fct hydride with an axial ratio of c/a < 1 ; and g, an fct metastable hydride with an axial ratio of c/a > 1. Above the eutectoid temperature, the phase boundaries between the a phase and the two- phase (a + b) region are delineated by temperature-composition values obtained from a composite set of isotherms. The a/(a + b) boundary has been reported to have a retrograde character [78Gab]. The assessed phase diagram for the Ti-H system represents projections of a P-T- X surface on the T-X plane and the P-X plane, respectively, where P is the pressure (in pascals), T is the temperature (in Kelvin and degrees Celsius), and X is the hydrogen concentration, expressed as X = H/T, the atomic ratio. The present diagram is based primarily on the work of [50Mcq], updated with review of the literature [60Bec, 83Dan, 84Num]. [83Sha] reported that at 50 MPa the melting point of Ti decreases as a consequence of the dissolved H. The most significant change in the melting point was observed between 10 and 25 MPa (around 100 C). At the maximum H concentration, this was ~130 C. At this pressure, solid Ti dissolves around 40 at.% of H, whereas the solubility in liquid Ti is ~70 at.%. [84Num] reported that a new fct (c/a = 1.09) phase precipitated when samples were charged with H or D by the gas-equilibrium method, kept at 500 C for about 10 h, and subsequently cooled at a rate of approximately 1 C/min. Thin plane and slightly bent platelets were observed to precipitate in prism habit planes {0110} and near-basal habit planes {0225}, respectively. [80Mey] reported a substantial increase in the superconducting transition temperature (Tc) in samples prepared by low-temperature implantation of H (D) in Ti foils (Tc = 0.4 K for pure Ti). The superconducting transition temperature increased with increasing implantation doses up to 4.95 K (4.89 K for D) and saturated at H or D concentrations of x = 0.15 с 0.02. According to later work [82Hem], the observed enhancement vanished with annealing of the samples to 300 K. [68Fri] reported that magnetic susceptibility increased strongly as a function of H concentration, as the composition x = 2 was reached. [53Trz] reported that magnetic susceptibility reached a maximum at x = 1.8, then decreased slightly up to x = 1.9, and finally increased. 50Mcq: D. McQuillan, Proc. Roy. Soc. (London), Ser. A, 204, 309-322 (1950). 53Trz: W. Trzebiatowski and B. Stalinski, Bull. Acad. Pol. Sci. Ser. Sci. Math. Astron. Phys., 1, 131-136 (1953). 60Bec: R.L. Beck, USAEC Rep. LAR-10, Denver Research Institute, 60-65, 77-80 ( Nov 1960). 68Fri: R.C. Frish and R.A. Forman, J. Chem. Phys., 48, 5187-5190 (1968). 78Gab: R.M. Gabidulin, B.A. Kolachov, A.A. Bukhanova, and E.V. Shchekoturova, Titanium and Titanium Alloys: Scientific and Technological Aspects, Proc. 3rd Int. Conf., Moscow, 1976, Vol. 2, A. Belov, Ed., 419-428 (1978) in Russian; TR: Vol. 2, W.J. Case, Ed., Plenum Press, New York, 1365-1375 (1982). 80Mey: J.D. Meyer and B. Stritzker, Physics of Transition Metals, 1980, Proc. Intl. Conf., Univ. of Leeds, P. Rhodes, Ed., Conference Series Number 55, The Institute of Physics, Bristol and London (1980). 82Hem: R. Hemplemann, D. Richter, and B. Strizker, J. Phys. F, Met. Phys., 12, 79-86 (1982). 83Dan: P. Dantzer, J. Phys. Chem. Solids, 44, 913-923 (1983). 83Sha: V.I. Shapovalov, N.P. Serdyuk, and A.L. Titkov, Izv. V.U.Z. Tsvetn. Metall., (6), 74-78 (1983) in Russian. 84Num: H. Numakura and M. Koiwa, Acta Metall., 32, 1799-1807 (1984). Published in Phase Diagrams of Binary Titanium Alloys, 1987, and Bull. Alloy Phase Diagrams, 8(1), Feb 1987. Complete evaluation contains 5 figures, 12 tables, and 123 references. 1