Фазовая диаграмма системы Au-Ca

К оглавлению: Другие диаграммы (Others phase diargams)

Au-Ca (Gold-Calcium) H. Okamoto, T.B. Massalski, C.B. Alcock, and V.P. Itkin The assessed Au-Ca phase diagram is based on the work of [34Wei]. Recent investigations [64Rau, 80Not] strongly suggested the necessity for further modifications of the diagram, but there are not enough new data to justify a change in the form of the phase boundaries. The equilibrium phases are (1) the liquid, L; (2) the fcc terminal solid solution, (Au), having a maximum solid solubility of less than 1.8 at.% Ca in (Au); (3) the bcc and fcc terminal solid solutions, (bCa) and (aCa), having a maximum solid solubility of ~ 4.5 at.% Au in (bCa) at 658 C; and (4) several intermediate phases, Au4Ca (and/ or Au5Ca, and/or Au9Ca2), Au3Ca (or Au7Ca2), Au2Ca, Au9Ca10 (AuCa or AuCa1.11), Au3Ca4, and AuCa2. The Au2Ca, Au9Ca10, and (Ca) phases undergo polymorphic transitions. Thermal and metallographic observations by [34Wei] clearly indicate that the Au-richest intermetallic phase is Au4Ca. X-ray and superconductivity measurements by [64Rau] suggested that the Au-richest phase is Au5Ca. According to the emf measurements of [80Not], the existence of only one phase, Au5Ca, was observed. [85Alq] reported two compounds, Au5Ca and Au9Ca2, in this composition range. It is uncertain which phases actually exist in this range. The thermodynamic properties of the Au-Ca system were studied by [80Not] by an electrochemical method at 800 to 1000 K. 34Wei: F. Weibke and W. Bartels, Z. Anorg. Allg. Chem., 218, 241-248 (1934) in German. 64Rau: Ch.J. Raub and D.C.Hamilton, J. Less-Common Met., 6, 486-488 (1964). 80Not: M. Notin, B.D. Djamshidi, and J. Hertz, Thermochim. Acta, 38(2), 173- 179 (1980) in French. 85Alq: R. Alqasmi and J.J. Egan, paper presented at the 114th TMS-AIME Annual Meeting, New York, (1985). Published in Phase Diagrams of Binary Gold Alloys, 1987. Complete evaluation contains 1 figure, 3 tables, and 10 references. 1