The isothermal section phase diagram of the Sm-Fe-Ni ternary system at 800 °C

Abstract

Isothermal section at 800 °C of the ternary Sm-Fe-Ni system was established in the whole concentration range, by means of powder X-ray diffraction and scanning electron microscopyenergy dispersive X-ray spectroscopy (SEM/EDS). All measured compositions and unit-cell refinements were performed at room temperature from quenched samples annealed at 800 °C for one week. Ten binary compounds and α(Fe1−x Nix) (Im−3m-W type structure) have been confirmed.The SmNi5−xFex (P6/mmm-CaCu5 type structure) was found to have a solubility range from 0 to 50 at% Fe. The maximum solubility at 800 °C of Fe in Sm2Ni7−xFex (P63/mmc-Ce2Ni7 type structure), SmNi3−xFex (R3¯m-PuNi3 type structure) and SmNi2−xFex (Fd−3m-MgCu2 type structure) are about 2.7 at% Fe, 40 at% Fe and 6.66 at% Fe, respectively. The homogeneity domain of Sm2Fe17−xNix (R3¯m-Th2 Zn17 type structure) ranges from 0 to 21.05 at% Ni. The XRD and the SEM/EDS analysis show that there are no solubility of Fe in the Sm2 Ni17, Sm5Ni19 and SmNi. The same analysis show that there are no solubility of Ni in the SmFe2 and SmFe3 and no ternary compound was found in all ternary alloy samples. The addition of Ni in the Sm-Fe system did not stabilize the ThMn12 type structure.