Фазовая диаграмма системы Ce-Pr

К оглавлению: Другие диаграммы (Others phase diargams)


Ce-Pr (Cerium-Praseodymium) K.A. Gschneidner, Jr. and F.W. Calderwood The assessed phase diagram for the Ce-Pr system is based primarily on the work of [80Alt]. Melting and transition temperatures of the pure component metals have been adjusted to conform with the accepted values of [Gschneidner]. Because the two-phase field is so narrow, the liquidus and solidus were drawn as a single straight line. [80Alt] studied the Ce-Pr alloy system using electrical resistivity, X-ray diffraction, and DTA techniques. For the most part, standard commercial material was used, but some relatively pure Pr was used in the DTA measurements. Their electrical resistivity curves for the Pr sample indicated only one solid phase transformation (dcph <259> bcc), whereas the curves for Ce and the Ce-Pr alloys exhibited two transitions, dcph <259> fcc (below 61 C for pure Ce) and fcc <259> bcc. The hysteresis that accompanied the dcph <259> fcc transition increased as the Ce content increased. An X-ray diffraction study [80Alt] on powders annealed at 600 C for 2 h and quickly cooled to room temperature showed that (a) alloys in the range 0 to 65 at.% Pr have the fcc structure; (b) alloys in the range 74 to 100 at.% Pr have the dcph structure; and (c) alloys containing 66 to 74 at.% Pr contained both dcph and fcc phases. [80Alt] found considerable hysteresis associated with the fcc <259> dcph transformation in Ce-rich alloys, which they associated with a change in the transformation mechanism from a martensitic to a diffusion-controlled process. They observed a rapid nonlinear increase for the temperature dependence of the solvus lines that separate the fcc from the dcph phase regions. They postulated that either the dcph + fcc phase field meets the bcc + fcc phase field just before 100 at.% Pr to yield a high-temperature eutectoid or peritectoid reaction, or that the dcph <259> fcc transition occurs in commercial Pr just below a bcc <259> fcc transition. [61Gsc] investigated the effect of alloying on the g <259> d transition temperature of Ce and found that an addition of 2 at.% Pr lowers this transition temperature. At high pressures, this addition of Pr increased transformation pressure of pure Ce. 61Gsc: K.A. Gschneidner, Jr., R.R. McDonald, and R.O. Elliott, Phys. Rev. Lett. , 6, 218 (1961). 80Alt: M. Altunbas and I.R. Harris, J. Mater. Sci., 15, 693 (1980). Published in Bull. Alloy Phase Diagrams, 3(2), Sep 1982. Complete evaluation contains 2 figures and 8 references 1