Фазовая диаграмма системы In-Tl

К оглавлению: Другие диаграммы (Others phase diargams)

In-Tl (Indium-Thallium) H. Okamoto The assessed In-Tl phase diagram is based on the work of numerous investigators [40Val, 48Kle, 50Gut, 50Mak, 51Gei, 52Sto, 53Bur, 55Moo, 63Mey, 65Luo, 66Adl, 68Pah, 68Pol, 78Nit, 78Pat] and on thermodynamic modeling. It does not represent the equilibrium state of the system regarding the a <259> ( In) martensitic transformation. True equilibrium between (In) and a and between (In) and (aTl) appears to be difficult to attain. The transition between a and (In) usually is regarded as martensitic, because the a + (In) two-phase field was believed to be very narrow or nonexistent. Either hysteresis of the martensitic transformation or existence of a two- phase field along the a/(In) metastable martensitic transition line was found only at low temperatures (<-100 C). However, the present thermodynamic calculation indicates that the stable a + (In) two-phase field is by no means narrow. The phase boundary between a and (In) was investigated extensively by [50Gut], [55Moo], [63Mey], [65Luo], [66Adl], [68Pah], [68Pol], and [78Pat]. The behavior of the metastable martensitic transformation cannot be represented by a single line in the composition range ~25 to 31 at.% Tl, where the temperature difference between the beginning and the completion of the martensitic transformation on cooling is prominent and becomes larger as the Tl concentration increases. Only the data for beginning temperatures of the martensitic transformation are shown in the assessed diagram. The transition of (In) to a on heating appears to be more complex. The mechanism of the fcc a <259> fct (In) transition was speculated by many investigators. Although thermodynamic principle requires the existence of a two-phase fcc + fct field in the stable state, no concrete experimental evidence is available. Some investigators arrived at a conclusion that the fct and fcc phases are contiguous. [50Mak] considered the transition to be continuous, because no two-phase region was found. [50Gut] proposed that the transition is second or higher order, because all X-ray diffraction patterns of alloys with different composition at room temperature contained only lines from one structure or the other. On the other hand, based on the data of [50Gut] and by analogy with other systems, [51Gei] considered that [50Gut] could not detect the two-phase field because it is very narrow. Although not detected experimentally, [63Mey] and [ 66Adl] presumed in their diagrams the existence of the two-phase field of about 2 at.% width at all temperatures down to 0 K. [68Pah] proposed the width to be ~0.5 at.% on the basis of their thermal expansion data. Based on the superconducting temperature measurements, [65Luo] speculated the possibility of a two-phase field region existing from 29 to 31 at.% Tl at very low temperatures. The evaluator considers the form of stable (In) + a two-phase field to be different from all of the above. If the two-phase field is very narrow at all temperatures from the melting point to 0 K, the Gibbs energy curves for fct and fcc phases must be almost identical in the same temperature range. However, this is very unlikely, because even the lattice stability parameters for both phases of In are not very similar. 40Val: S. Valentiner, Z. Metallkd., 32, 244-248 (1940) in German. 48Kle: W. Klemm, L. Klemm, E. Hoffman, H. Volk, E. Orlamunder, and H. Klein, Z. Anorg. Chem., 256, 239-252 (1948) in German. 50Gut: L. Guttman, Trans. AIME, 188(12), 1472-1477 (1950). 50Mak: E.S. Makarov, Izv. Akad. Nauk. SSSR, Chem. Sci., (5), 485-491 (1950) in Russian. 51Gei: A.H. Geisler and D.L. Martin, Discussion, Trans. AIME, 191, 1056-1057 ( 1951). 52Sto: J.W. Stout and L. Guttman, Phys. Rev., 88(4), 713-714 (1952). 53Bur: M.W. Burkart and T.A. Read, Trans. AIME, 197(11), 1516-1524 (1953). 55Moo: A. Moor, J. Graham, G.K. Williamson, and G.V. Raynor, Acta Metall., 3( 11), 579-589 (1955). 63Mey: R.W. Meyerhoff and J.F. Smith, Acta Metall., 11(6), 529-536 (1963). 65Luo: H.L. Luo, J. Hagen, and M.F. Merrian, Acta Metall., 13, 1012-1013 (1965) . 66Adl: P.N. Adler and H. Margolin, Acta Metall., 14(12), 1645-1658 (1966). 68Pah: J.E. Pahlman and J.F. Smith, J. Less-Common Met., 16(4), 397-405 (1968). 68Pol: J.T.A. Pollock and H.W. King, J. Mater. Sci., 3(4), 372-379 (1968). 78Nit: O. Nittono and Y. Koyama, J. Jpn. Inst. Met., 42(1), 56-63 (1978) in Japanese. 78Pat: J. Patel and S. Ahmed, Met. Sci. J., 12(3), 147-150 (1978). Submitted to the APD Program. Complete evaluation contains 9 figures, 7 tables, and 59 references. Special Points of the In-Tl System