Фазовая диаграмма системы Hf-Sn

К оглавлению: Другие диаграммы (Others phase diargams)

Hf-Sn (Hafnium-Tin) H. Okamoto The assessed Hf-Sn phase diagram is based primarily on the data of [64Was] for 0 to 37.5 at.% Sn and on [71Tsy] for 60 to 100 at.% Sn. The equilibrium phases are (1) the liquid, L; (2) the bcc W-type terminal solid solution, (bHf); (3) the cph Mg-type terminal solid solution, (aHf); (4) hexagonal Mn5Si3-type Hf5Sn3; (5) hexagonal Hf5Sn4; (6) cubic FeSi-type HfSn; (7) hexagonal CrSi2- type HfSn2; (8) the tetragonal terminal solid solution, (bSn); and (9) the diamond cubic terminal solid solution (aSn). The melting point of bHf is 2231 C [Melt]. The liquidus and solidus of (bHf) measured by [71Tsy] are not acceptable because of a large disagreement in the melting point of bHf (observed at 2400 C; purity of the specimen and/or experimental accuracy are suspicious) with the assessed value. The assessed liquidus and solidus boundaries are based on [64Was], with some modifications in the melting point of bHf. The L = (bHf) + Hf5Sn3 eutectic point is at 20.5 at.% Sn and 1725 с 25 C [64Was]. the maximum solubility of Sn in (bHf) was reported as ~16 at.% [64Was] (17 at.% according to [71Tsy]). The (bHf) = (aHf) + Hf5Sn3 eutectoid point is at ~15 at.% Sn and ~1680 C [ 64Was]. The bHf = aHf allotropic transformation temperature is 1743 C. A significant amount of Sn dissolves in (aHf), because the lattice parameters of (aHf) in 20 at.% Sn two-phase alloy are considerably different from those of pure aHf [ 60Bol2]. In agreement, [64Was] and [71Tsy] reported maximum solubility of about 14 at.% Sn in (aHf). The assessed (aHf) solvus is adopted from [64Was]. The melting point of Hf5Sn3 is 1735 с 25 C [71Tsy]. However, the assessed L = (bHf) + Hf5Sn3 eutectic point (20.5 at.% Sn and 1725 C) requires a somewhat higher temperature for the congruent melting point (probably >1900 C). The melting temperature of Hf5Sn4 and its relationship with other phases are unknown. HfSn forms by sintering only at about 1000 C, and it does not form if the temperature is higher or lower [64Sch]. The stability of HfSn and the relationship with other phases are unknown. The L + Hf5Sn3 = HfSn2 peritectic temperature is 1530 с 25 C [72Tsy]. However, Hf5Sn4 may be involved in the reaction. The melting point of bSn is 231.9681 C [Melt]. The bSn = aSn allotropic transformation temperature is 13 C. The L = HfSn2 + (bSn) eutectic temperature is 230 с 5 ш C [71Tsy]. 57Smi: J.F. Smith, USAEC, ISC-835, 33 p (1957); quoted in [Elliot]. 60Bol1: H. Boller, H. Nowotny, and A. Wittmann, Monatsh. Chem., 91(4), 736 ( 1960) in German. 60Bol2: H. Boller, H. Nowotny, and A. Wittmann, Monatsh. Chem., 91(6), 1174- 1184 (1960). 61Bai: D.M. Bailey and J.F. Smith, Acta Crystalogr., 14, 57-58 (1961). 62Sch: K. Schubert, H.G. Meissner, M. Potzschke, W. Rossteutscher, and E. Stoltz, Naturwissenschaften, 49(3), 57 (1962) in German. 64Sch: O. Schob and E. Parthe, Acta Crystallogr., 17, 452-453 (1964). 64Was: G.E. Wasielewski, USAEC, KAPL-3019, 54 p (1964); quoted in [Shunk]. 65Rie: W. Rieger, H. Nowotny, and F. Benesovsky, Monatsh. Chem., 96, 232-241 ( 1965) in German. 65Ros: W. Rossteutscher and K. Schubert, Z. Metallkd., 56(11), 813-822 (1965) in German. 71Tsy: I.A. Tsyganova, M.A. Tylkina, and E.M. Savitsky, Izv. Akad. Nauk SSSR, Met., (3), 188-191 (1971) in Russian; TR: Russ. Metall., (3), 129-131 (1971). Submitted to the APD Program. Complete evaluation contains 1 figure, 2 tables, and 10 references. 1