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 ⩽ 33.3 at.% Sm0.5Nd0.5were determined in an isothermal section at 1073 K and a vertical section RFe2–RCo2by 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)17phase dissolves less than 4 at.% Co at 1073 K. However, the (Sm, Nd)2(Fe, Co)7phase in R2(Fe1–xCox)7alloys dissolves about 15 at.% Fe at 1073 K.