Investigation of phase equilibria in the Ce-Co-Fe system during solidification

Abstract Phase transformations in the Ce-Co-Fe ternary system have been studied using DTA, X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). No ternary compounds have been identified in this system. Liquidus and solidus projections and a Scheil diagram for solidification were constructed. At the solidus temperatures two continuous solid solutions form: (1) between isostoichiometric compounds Ce 2 Fe 17 (Zn 17 Th 2 -type structure, hR57-R-3m ) and Ce 17 Co 2 (Th 2 Ni 17 -type structure, hP38-P6 3 /mmc ) and (2) between the Laves phases CeFe 2 and CeCo 2 (MgCu 2 -type structure, cF24-Fd-3m ). Among the binary system-based phases, CeCo 3 has the widest homogeneity region and dissolves up to 58 at% Fe at the solidus temperature. The homogeneity regions of the remaining phases are smaller. Five three-phase fields in the solidus surface result from four transition type and one eutectic invariant four-phase equilibria.