Phase Equilibria in the Ternary System Fe-Gd-Mo at 600 �C

Abstract

Phase equilibria in the ternary system Fe-Gd-Mo at 600 °C were determined. The phase composition for different element concentrations were quantitatively determined from the diffraction patterns by means of the multi-phase Rietveld-refinement as well as through evaluation of the microstructure images obtained by the scanning electron microscopy. Both methods are compared with each other with respect to their precision and limitations. The complete isothermal section at 600 °C includes one ternary phase τ (ThMn12-type of structure), four pseudo-binary phases (Fe,Mo)17Gd2, (Fe,Mo)23Gd6, (Fe,Mo)3Gd and (Fe,Mo)2Gd and binary phases Fe2Mo and μ-(Fe,Mo). The ternary phase τ forms the tie-lines with the solid solutions α-Fe, (Mo)-, Fe2Mo and μ-(Fe,Mo) phases as well as with the pseudo-binary Fe-Gd compounds. Three phases (Fe,Mo)2Gd, (Mo) and Gd coexist in a wide concentrations range. The homogeneity region of the ternary phase τ as well as the solubilities of the third element in the binary phases were determined.