Фазовая диаграмма системы As-Ni

К оглавлению: Другие диаграммы (Others phase diargams)


As-Ni (Arsenic-Nickel) M. Singleton and P. Nash The Ni-As system consists of four intermetallic compounds (Ni5As2, Ni11As8, NiAs, and NiAs2), two of which are stoichiometric (Ni11As8 and NiAs2); three eutectic reactions; one peritectic reaction; and a terminal solid solution of As in (Ni). No data regarding the As-rich end of the diagram are available. The assessed Ni-As phase diagram is based on the work of [Hansen] and [Elliott] , with some modifications. The melting point of pure Ni has been taken as 1455 C [Melt]. A eutectic reaction occurs at 23.4 at.% As and 897 C, between Ni5As2 and the Ni-rich solid solution [07Fri]. In the present diagram, the liquidus and solidus have been drawn subsequent to the establishment of compound locations, except for the liquidus between pure Ni and the Ni-rich eutectic at 23.4 at.% As, and the Ni-rich solidus and solvus. The maximum solubility of As in (Ni) is estimated to be 4.5 at.% As. The melting points of Ni5As2 and NiAs were determined by [07Fri] as 998 с 3 C and 970 с 3 C, respectively. [60Hey] reported the existence of a stoichiometric NiAs2 phase with a eutectic between this phase and NiAs located at 853 C and 58 at.% As. Because the melting point of NiAs2 is not available in the literature, the line representing the compound is dashed at temperatures higher than 853 C. On the As-rich side of the eutectic reaction at 37.2 at.% As and 804 C, some controversy exists over the phases and reactions that occur. Ni11As8 is formed through a peritectic reaction of NiAs, with the melt at approximately 850 C [ 57Hey]. A Ni-rich compound, Ni5As2, has been reported at approximately 28.5 at.% As, with a solubility range of 0.65 at.% [73Kje]. The solubility range of the congruently melting NiAs phase extends from 50 to 51.3 at.% As [57Hey]. The Ni5As2 phase is hexagonal, the Ni11As8 compound is tetragonal, and NiAs2 is polymorphic. The high-temperature modification, bNiAs2 , ha s an orthorhombic marcasite structure. The low-temperature modification, aNiAs2, is also orthorhombic. Alloys exhibiting the compositions Ni0.766As0.234, Ni0.740As0.260, and Ni0. 820As0.180 rapidly cooled after melting (splat quenched) by [83Elb] all revealed crystalline structures consisting of Ni5As2 and a solid solution of As in (Ni). Splat quenching of Pd-rich Pd-As alloys and Pt-rich Pt-As alloys lowered the effective eutectic temperature in these systems by 560 and 720 K, respectively, producing metallic glasses. The effective eutectic temperature in the Ni-As system was lowered to a much lesser extent (by 280 K), thereby explaining why amorphous structures could not be produced. 07Fri: K. Friedrich, Metallurgie, 5, 598 and 601-603 (1907). 57Hey: R.D. Heyding and L.D. Calvert, Can. J. Chem., 35, 1205-1215 (1957). 60Hey: R.D. Heyding and L.D. Calvert, Can. J. Chem., 38, 313-316 (1960). 73Kje: A. Kjekshus and K.E. Skaug, Acta Chem. Scand., 27, 582-588 (1973). 83Elb: M. El-Boragy, M. Ellner, and B. Predel, Z. Metallkd., 74, 545-548 (1983) in German. Published in Phase Diagrams of Binary Nickel Alloys, 1991, and Bull. Alloy Phase Diagrams, 8(5), Oct 1987. Complete evaluation contains 2 figures, 2 tables, and 18 references. 1