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

Abstract

Phase equilibria in the Fe–Mn–Ce system at 900 °C were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. Using the results an isothermal section at 900 °C for this system was constructed covering the whole concentration range. The stability of the ternary compounds Fe11Mn6Ce2 (τ1) and Fe5Mn7Ce (τ2) at 900 °C, identified previously, was confirmed. The ternary compound τ1 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 °C. The ternary compound τ2 is located along a line with a constant Ce concentration of 8 at.%. Its homogeneity range extends from 35 up to ∼70 at.% Mn at 900 °C. The phases βFe17Ce2 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 βFe17Ce2 and Fe2Ce were established to be 18 and ∼28 at.%, respectively.At 900 °C the liquid phase is stable in the Fe–Mn–Ce system. The isothermal section is characterized by eight three-phase regions: (αFe) + (γFe,Mn) + (βFe17Ce2), (γFe,Mn) + (Fe2Ce) + (βFe17Ce2), (γFe,Mn) + (Fe2Ce) + τ1, (γFe,Mn) + τ1 + τ2, τ1 + τ2 + (Fe2Ce), (γFe,Mn) + (βMn) + τ2, L + (βMn) + τ2 and L + τ2 + (Fe2Ce) plus the corresponding two-phase regions.