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

Phase equilibria in the Fe-Mn-Ce system at 900 degrees C were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. Using the results an isothermal section at 900 degrees C for this system was constructed covering the whole concentration range. The stability of the ternary compounds Fe11Mn6Ce2 (tau(1)) and Fe5Mn7Ce (tau(2)) at 900 degrees C, identified previously, was confirmed. The ternary compound tau(1) is located along a line with a constant Ce concentration of 9.6 at.% and its homogeneity range extends from 20 up to 34 at.% Mn at 900 degrees C. The ternary compound tau(2) is located along a line with a constant Ce concentration of 8 at.%. Its homogeneity range extends from 35 up to similar to 70 at.% Mn at 900 degrees C. The phases beta Fe17Ce2 and Fe2Ce, both of which dissolve appreciable quantities of Mn, are located along lines with constant concentrations of Ce of 10.8 and 33 at.%, respectively. The solubilities of Mn in beta Fe17Ce2 and Fe2Ce were established to be 18 and similar to 28 at.%, respectively. At 900 degrees C the liquid phase is stable in the Fe-Mn-Ce system. The isothermal section is characterized by eight three-phase regions: (alpha Fe) + (gamma Fe, Mn) + (beta Fe17Ce2), (gamma Fe, Mn) + (Fe2Ce) + (beta Fe17Ce2), (gamma Fe, Mn) + (Fe2Ce) + tau(1), (gamma Fe, Mn) + tau(1) + tau(2), tau(1) + tau(2) + (Fe2Ce), (gamma Fe, Mn) + (beta Mn) + tau(2), L + (beta Mn) + tau(2) and L + tau(2) + (Fe2Ce) plus the corresponding two-phase regions. (C) 2015 Elsevier B.V. All rights reserved.