Фазовая диаграмма системы Mn-Ti

К оглавлению: Другие диаграммы (Others phase diargams)


Mn-Ti (Manganese-Titanium) J.L. Murray The equilibrium solid phases of the Ti-Mn system are: (1) the bcc (bTi) and ( dMn) solid solutions, stable in pure Ti above 882 C and in pure Mn between 1246 and 1138 C; (2) the Ti-rich low-temperature cph (aTi) solid solution; (3) the fcc (gMn) solid solution stable in pure Mn between 1100 and 1138 C; (4) the complex cubic (bMn) solid solution, stable in pure Mn between 727 and 1100 C; (5) the complex cubic low-temperature (aMn) solid solution; (6) near- equiatomic compounds aTiMn and bTiMn; (7) TiMn2, a Laves phase of the MgZn2 type with a broad homogeneity range, which melts congruently at 1325 C; (8) the compound TiMn3, stable between about 950 and 1250 C; and (9) the compound TiMn4 of composition 81.5 at.% Mn, stable between approximately 930 and 1230 C. The crystal structures of TiMn3 and bTiMn, the positions of several phase boundaries, and the temperatures of several three-phase equilibria have not yet been determined experimentally or fully confirmed. The assessed phase diagram is drawn from a calculation of the diagram from Gibbs energies optimized with respect to select phase diagram data. The (bTi) liquidus and solidus are based on thermal analysis, microstructural, and incipient melting studies [53May]. An uncertainty of about с25 C is estimated for these boundaries. The eutectic temperature is based on thermal analysis studies of [57Hel] (1181 с 2 C) and [53May] (1175 C). The assessed (bTi) transus lies between determinations of [51Mcq] and [53May] and is based on optimization of Gibbs energies with respect to the data of [ 53May]. The belief that the observed transus temperatures of [53May] are too high is supported by the observation by [79Sal] that a 9 at.% Mn alloy was single-phase (bTi) at 700 C. [53May] found the solubility of Mn in (aTi) to be 0.4 с 0.1 at.% at the eutectoid temperature. There has been controversy about the equiatomic compounds, because it was originally assumed that only one phase existed between the (Ti) solutions and TiMn2. There are two phases of near- equiatomic composition, aTiMn stable only to about 950 C and bTiMn stable to at least 1150 C and therefore probably to the melt [62Wat]. The L + TiMn2 = b TiMn peritectic reaction is placed at 1200 C based on thermal analysis on cooling [53May]. The (bTi) + bTiMn = aTiMn peritectoid reaction occurs between 930 and 960 C [62Wat]. The compositions of bTiMn and aTiMn are 52 and 50.5 at.% Mn, based on the X-ray and microstructural work of [62Wat]. The TiMn2 liquidus was determined by [53May] and [57Hel] using thermal analysis. The data of [57Hel] are preferred because of the care taken to avoid contamination and attention to the possibility of composition changes during melting. The existence of one or more intermetallic compounds between TiMn2 and pure Mn was deduced from thermal analysis data [57Hel]. X-ray and metallographic work [ 61Wat] identified the two phases as TiMn3 and TiMn4 (about 81.5 at.% Mn), and the reactions were interpreted as L + TiMn2 = TiMn3 and L + TiMn3 = TiMn4. The (dMn) liquidus and solidus were investigated by [57Hel] and [58Mur]. Both authors showed the formation of (dMn) by a eutectic reaction. The effect of Ti additions on the allotropic transformation of Mn was investigated by [57Hel] and [60Sav] using thermal analysis. There are disagreements between the two investigations. The work of [57Hel] is preferred because of the care to maintain and to document sample purity. The calculated phase boundaries lie within about 5 C and 1 at.% of the input data and were used to draw the assessed diagram. The (aMn) boundaries may require significant modifications as further experimental data on the extent of the ( aMn) region become available. In studies to measure the start temperature for the martensite (bTi) to (aTi) transformation, (bTi) was found to be retained to room temperature when the Mn content exceeds about 4 to 5 at.% [53Duw, 58Age]. w can form either during quenching from the (bTi) region or during aging of metastable (bTi) alloys below approximately 400 C [69Hic]. [58Age] reported as-quenched w phase between 2.6 and 4.8 at.% Mn. When w phase forms during aging, the compositions of w and (bTi) approach a metastable equilibrium at 5.1 and 19.1 at.% Mn [ 69Hic]. 51Mcq: A.D. McQuillan, J. Inst. Met., 80, 363-368 (1951). 53Duw: P. Duwez, Trans. ASM, 45, 934-940 (1953). 53May: D.J. Maykuth, H.R. Ogden, and R.I. Jaffe, Trans. AIME, 197, 225-231 ( 1953). 57Hel: A. Hellawell and W. Hume-Rothery, Philos. Trans. R. Soc. (London), 249, 417-454 (1957). 58Age: N.V. Ageev and Z.M. Smirnova, Titanium and Its Alloys, Akad. Nauk SSSR, 1, 17-24 (1958). 58Mur: Y. Murakami and T. Enjyo, J. Jpn. Inst. Met., 22, 261-265 (1958) in Japanese. 60Sav: E.M. Savitskii and Ch.V. Kopetskii, Zh. Neorg. Khim., 5, 2422-2434 ( 1960); TR: Russ. J. Inorg. Chem., 5, 1173-1179 (1960). 61Wat: R.M. Waterstrat, Trans. AIME, 221, 687-690 (1961). 62Wat: R.M. Waterstrat, B.N. Das, and P.A. Beck, Trans. AIME, 224, 512-518 ( 1962). 69Hic: B.S. Hickman, Trans. AIME, 245, 1329-1336 (1968). 79Sal: Y. Saleh and H. Margolin, Acta Metall., 27, 535-544 (1979). Published in Phase Diagrams of Binary Titanium Alloys, 1987. Complete evaluation contains 6 figures, 6 tables, and 36 references. Special Points of the Ti-Mn System