Phase equilibria in the Ce-Co-Fe-system at 900 °C

The Ce-Co-Fe phase diagram was investigated for the whole concentration range at 900 °C, using X-Ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). An isothermal section at this temperature was constructed. Two continuous solid solutions Ce2(Co,Fe)17 (Th2Zn17-type structure, hR57-R-3m) and Ce(Co,Fe)2 (MgCu2-type structure, cF24-Fd-3m), found by us both at the solidus temperatures and at 900 °C, contain 11 and 33.3 at.% Ce, respectively, due to mutual substitution of Fe and Co atoms. The liquid phase is present in the system at 900 °C. The isothermal section at this temperature is characterized by the five three-phase regions (αFe) + (αCo) + Ce2(Co,Fe)17, Ce5Co19 + CeCo5 + Ce2Co7, CeCo5 + Ce2(Co,Fe)17 + Ce2Co7, Ce2Co7 + Ce2(Co,Fe)17 + CeCo3 and CeCo3 + Ce2(Co,Fe)17 + Ce(Co,Fe)2 and associated two-phase fields. CeCo3 and Ce2Co7 show the widest homogeneity regions and dissolve up to 49 at.% and 21 at.% Fe respectively. The solubility of Fe in the other crystalline phases is smaller.