Фазовая диаграмма системы B-Cu

К оглавлению: Другие диаграммы (Others phase diargams)


B-Cu (Boron-Copper) D.J. Chakrabarti and D.E. Laughlin The equilibrium phases of the Cu-B system are (1) the fcc terminal solid solution, (Cu), with a limited maximum solubility of B of ~0.29 at.%; and (2) the terminal solid solution, (B), having several allotropic modifications, with the b-rhombohedral form dominant at elevated temperatures and the b- tetragonal and, possibly, a-rhombohedral and a-tetragonal forms stable at low temperatures. The stability ranges for these phases are not well defined. The maximum recorded solubility of Cu in (B) is between 3.65 and 4.17 at.%, with retrograde characteristics at elevated temperatures. The Cu-B phase diagram is of the simple eutectic type with no intermediate phases present. The high melting point of B and its strong affinity for oxygen in the liquid state presented difficulties in alloy preparation and in identification of equilibrium phases in earlier studies [Hansen]. The occurrence of a eutectic reaction between the Cu-rich terminal solid solution and the compound CuB22 was reported by [54Lih]. Subsequent studies by [65Smi], [65Wal], and [70Rex] confirmed the occurrence of the eutectic reaction, but the constituent phases were shown to be the terminal solutions of Cu with that of B and not with CuB22. It was concluded that CuB22 does not occur as a separate equilibrium phase. The work of [74Hig] and [74Pit] were also reviewed in preparing the assessed diagram. The initial slope of the liquidus at the Cu end appears to be very sensitive to the presence of impurity elements; the magnitude of the slope increases with progressive purity of the melt. The liquidus boundaries at the Cu and B ends of the diagram were drawn by applying van't Hoff's relation to the initial slopes of the solidus curves. The data of [65Wal] for the B-rich compositions were incompatible with the initial slope requirements for the liquidus and were disregarded. The remainder of the liquidus was drawn based on the data of [65Wal] and [70Rex]. 54Lih: F. Lihl and O. Fleischl, Metall, 8, 11-19 (1954) in German. 65Smi: A.P. Smiryagin and O.S. Kvurt, Tr. Gos. Nauchn. Issled. Proektn. Inst. Splavov Obrab. Tsvetn. Metal., 24, 7-11 (1965). 65Wal: F. Wald and R. Stormont, J. Less-Common Met., 9, 423-433 (1965). 70Rex: J. Rexer and G. Petzow, Metall, 24, 1083-1086 (1970) in German. 74Hig: I. Higashi, Y. Takahashi, and T. Atoda, J. Less-Common Met., 37, 199- 204 (1974). 74Pit: J.P. Piton, G. Vuillard, and T. Lundstrom, C.R. Acad. Sci., Ser. C, 278, 1495-1496 (1974). Published in Bull. Alloy Phase Diagrams, 3(1), Jun 1982. Complete evaluation contains 2 figures, 4 tables, and 25 references. 1