Фазовая диаграмма системы N-Ta

К оглавлению: Другие диаграммы (Others phase diargams)


In-Ta (Indium-Tantalum) H. Okamoto The assessed In-Ta phase diagram is based partly on the experimental work of [ 82Vil]. The diagram proposed by [82Vil] showed that (In) and (Ta) are completely immiscible in both the liquid and the solid states. This was qualitatively in agreement with [69Das], who predicted the immiscibility of In and Ta in the liquid state. However, because the boiling point of In is lower than the melting point of Ta, liquid immiscibility is metastable and does not occur in the assessed diagram. Because of the refractory nature and the high melting point of Ta (3020 C [ Melt]), it is likely that the eutectic reaction observed by [82Vil] was actually the (In,s) <259> (In,L) melting process. If the observed low eutectic temperature is accepted, liquid (In) would dissolve more than 3 at.% Ta (assuming that the enthalpy of fusion of In is 3280 J/mol [83Cha]). However, the (metastable) immiscibility in the liquid state is a strong indication of very limited solubility of Ta in liquid (In). [74Die] estimated the solubility of Ta in liquid In between 327 and 967 C: log C = 0.2 - 4000/T, where C is at.% Ta and T is K. According to this expression, the eutectic composition is completely negligible (on the order of 10-9 at.% Ta). Therefore, the actual eutectic temperature must be very close to the melting point of In. No intermetallic phase was formed by 3 months of sintering an InTa3 powder mixture (particle size: In = 150 mm, Ta = 40 mm) at 500 C under 7 kbar [ 82Vil]. However, this observation does not preclude the existence of stable intermediate phases, because the reaction temperature adopted by [82Vil] may have been too low. [65Ram] found an AuCu type compound region in a cast alloy of nominal InTa3 composition, coexisting with an oxide phase. The existence and stability range of InTa3, however, have not been confirmed. The diagram of [82Vil] showed the L2 <259> L1 + (Ta) monotectic temperature as ~3000 C. No experimental data were given. Because the boiling point of In ( 2073 C) is lower than this temperature, the (In,g) phase should appear at l bar, as shown in the assessed diagram, instead of the monotectic reaction proposed by [82Vil]. 65Ram: A. Raman and K. Schubert, Z. Metallkd., 56(1), 44-52 (1965) in German. 69Das: C. Dasarathy, Trans. Metall. Soc. AIME, 245(9), 2015-2019 (1969). 74Die: E.N. Dieva, Physicochemical Studies of Liquid Metals and Alloys, V.G. Bamburov, Ed., Izd. Ural'sk. Nauch. Tsentra Akad. Nauk SSSR, Sverdlovsk, 105- 110 (1974) in Russian. 82Vil: P. Villars and K. Girgis, Z. Metallkd., 73, 169-171 (1982) in German. 83Cha: M.W. Chase, Bull. Alloy Phase Diagrams, 4(1), 123-124 (1983). Published in Bull. Alloy Phase Diagrams, 9(1) Feb 1988. Complete evaluation contains 1 figure, 2 tables, and 6 references. 1