Phase diagram of the Fe-Co-R system with R ≤ 33.3 at.% Sm0.5Nd0.5

Phase equilibria of the Fe-Co-R system with R less than or equal to 33.3 at.% Sm0.5Nd0.5 were determined in an isothermal section at 1073 K and a vertical section RFe2-RCo2 by using optical microscopy, X-ray diffraction analysis, electron probe microanalysis, and differential thermal analysis techniques. There are seven intermetallic phases: (Sm, Nd) (Fe, Co)(2), (Sm, Nd)(Fe, Co)(3), (Sm, Nd)(5)(Fe, Co)(17), (Sm, Nd)(2)(Fe, Co)(7), (Sm, Nd)(5)(Fe, Co)(19), (Sm, Nd)(Fe, Co)(5), and (Sm, Nd)(2)(Fe, Co)(17). The (Sm, Nd)(5)(Fe, Co)(17) phase dissolves less than 4 at.% Co at 1073 K. However, the (Sm, Nd)(2)(Fe, Co)(7) phase in R-2(Fe1-xCox)(7) alloys dissolves about 15 at.% Fe at 1073 K.