Фазовая диаграмма системы C-Ti

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C-Ti (Carbon-Titanium) J.L. Murray The condensed Ti-C system has been characterized from 0 to about 70 at.% C. In addition to the bcc (bTi) and cph (aTi) solutions, there is an equilibrium carbide, TiC, with the homogeneity range 32 to 48.8 at.% C. The carbide has another form, designated Ti2C, in which vacancies are ordered on the carbon sublattice [67Gor]. This ordered phase is not the same as that mentioned by [ Hansen]. The most important phase diagram investigations were conducted by [53Cad], [ 55Ogd], [56Wag], [59Bic], and [65Rud]. At higher temperatures, the assessed diagram is based on [65Rud]; at lower temperatures, it is based on [53Cad] and [56Wag]. A thermodynamic assessment was presented by [85Uhr], in which agreement is good between calculated and experimental diagrams; the assessed TiC liquidus is drawn from the calculations of [84Uhr]. [59Bic] estimated liquidus compositions by chemical analysis of the liquid held at temperature until the melt composition was changing only very slowly. These data imply a eutectic composition of about 4.5 at.% C. [65Rud] estimated the liquidus to be somewhat above the temperature at which the samples collapsed. [65Rud] placed the eutectic composition at slightly less than 2 at.% C, based on metallographic examination of as-cast alloys. They noted that the low carbon content of the eutectic and structural changes that occurred during quenching made the metallographic work difficult. The Ti-rich limit of the TiC phase field was determined metallographically by [ 53Cad] (38 at.% C at 920 C) and metallographically and from the melting point data by [65Rud] (32 at.% C at 1650 C). Reported congruent melting points of TiC range between 1940 and 3250 C. The value 3067 с 15 C [65Rud] is chosen for the assessed diagram. The reaction L = TiC + C (graphite) is placed at 2776 C, with the eutectic composition about 63 at.% C [65Rud]. No distinction has yet been made between equilibria involving TiC and those involving ordered Ti2C. [62Bit] found discontinuities in the magnetic susceptibility of TiC as a function of composition. [67Gor] performed neutron diffraction studies of alloys annealed between 1100 and 2000 C. Superlattice lines were found in the range 32 to 36 at.% C. At 33 at.% C, Ti2C was estimated to be stable up to about 1900 C. 53Cad: I. Cadoff and J.P. Nielsen, Trans. AIME, 197, 248-252 (1953). 55Ogd: H.R. Ogden, R.I. Jaffee, and F.C. Holden, Trans. AIME, 203, 73-80 (1955) . 56Wag: F.C. Wagner, E.J. Bucur, and M.A. Steinberg, Trans. ASM, 48, 742-761 ( 1956). 59Bic: R.L. Bickerdike and G. Hughes, J. Less-Common Met., 1, 42-49 (1959). 62Bit: H. Bittner and H. Goretzki, Monatsh. Chem., 93, 1000-1004 (1962) in German. 65Rud: E. Rudy, D.P. Harmon, and C.E. Brukl, AFML-TR-65-2, Part I, Vol. II ( 1965). 67Gor: H. Goretzki, Phys. Status Solidi, 20, K141-K143 (1967). 84Uhr: B. Uhrenius, Calphad, 8(2), 101-119 (1984). Published in Phase Diagrams of Binary Titanium Alloys, 1987. Complete evaluation contains 4 figures, 4 tables, and 43 references. Special Points of the Ti-C System