Фазовая диаграмма системы Ag-Nd

К оглавлению: Другие диаграммы (Others phase diargams)


Ag-Nd (Silver-Neodymium) K.A. Gschneidner, Jr. and F.W. Calderwood The assessed phase diagram of the Ag-Nd system is based on the work of [79Fer] for the region 0 to 30 at.% Nd and on the data of [79Fer] and [78Mul] for the remainder of the system. In addition, the melting points of Ag and Nd and the a = b transformation temperature of Nd have been adjusted to agree with the accepted values [Gschneidner]. The largest of these adjustments is in the a = b transformation temperature of Nd (raised from 847 to 863 C). To retain the same depression of this transition temperature with the addition of Ag to (bNd), the catatectic temperature has also been raised 16 C, from 725 to 741 C. The unexplained thermal effect at ~780 C between bAg2Nd and AgNd has been indicated as a dashed line [78Mul]. In Ag systems with a light lanthanide metal, [70Mcm] found that the Ag5RE phase was the form with the highest Ag content, but this compound did not form in the Ag-Nd system. Like other Ag51RE14 compounds, Ag51Nd14 crystallizes in the hexagonal structure with an Ag51Gd14-type unit cell. [74Fer] investigated this system as part of a study of the Ag-rare earth phase diagrams. The following phases occurred: Ag51Nd14 (melting point, 1025 с 10 C) , Ag2Nd (peritectic formation at 825 с 5 C), and AgNd (melting point, 952 с 10 C). Three eutectics were reported: (Ag)-Ag51Nd14 (803 с 5 C, 10.5 at.% Ag) , Ag2Nd-AgNd (810 с 5 C, 40.8 at.% Ag), and AgNd-(aNd) (640 с 5 C, 80 at.% Nd). Solubility of Nd in (Ag) was reported to be 0.2 to 0.25 at.% Nd at the eutectic temperature (808 с 3 C). The melting points reported for compositions in the vicinity of Ag51Nd14 were obtained on heating, because the cooling process is susceptible to supercooling. In the 27 to 50 at.% composition range, unexplained thermal effects were observed by [74Fer] at 783 с 5 C and at 650 с 10 C. These investigators reported that the Nd metal melted at 1017 C and underwent the a <259> b transformation at 847 C. The transformation temperature dropped to 725 C as the Ag concentration increased to about 4 to 5 at.%. The maximum solid solubility in (aNd) was reported to be about 1 at.% at 725 C. [78Sta] reported Ag3Nd as the Ag-rich phase, but [79Fer] preferred the Ag51RE14 stoichiometry over Ag3RE. 70Mcm: O.D. McMasters, K.A. Gschneidner, Jr., and R.F. Valentine, Acta Crystallogr., B26, 1224-1229 (1970). 74Fer: R. Ferro, A. Borsese, S. Delfino, R. Marazza, and A. Seminara, J. Less- Common Met., 35, 39-44 (1974). 78Mul: A.M. Mulokozi, I. Stapf, and E. Gebhardt, J. Less-Common Met., 57, 39 ( 1978). 78Sta: I. Stapf and E. Gebhardt, J. Less-Common Met., 58, 47-53 (1978). 79Fer: R. Ferro and S. Delfino, J. Less-Common Met., 68, 23-29 (1979). Published in Bull. Alloy Phase Diagrams, 6(1), Feb 1985. Complete evaluation contains 1 figure, 1 table, and 14 references. 1