The solid state phase equilibria in the Y-Fe-Ga ternary system at 800 °C were investigated by means of X-ray diffraction, scanning electron microscope (SEM) and quantitative electron probe microanalysis (EDS). The isothermal section of the Y-Fe-Ga ternary phase diagram contains 15 single phase-regions, 32 two phase-regions, 12 three phase-regions and one liquid area. The phase diagram at this temperature is characterized by the formation of ten binary stable phases. Among these, there are six extensions of the binary compounds Y 2 Fe 17 , YFe 3 , YFe 2 , YGa 2 , Y 3 Ga 5 and Y 5 Ga 3 into the ternary system Y 2 Fe 17− x Ga x ( x ≤ 2 ), YFe 3− x Ga x ( x ≤ 0.8 ), YFe 2− x Ga x ( x ≤ 0.14 ), YGa 2− x Fe x ( x ≤ 0.5 ), Y 3 Ga 5− x Fe x ( x ≤ 0.15 ) and Y 5 Ga 3− x Fe x ( x ≤ 0.1 ), respectively. The homogeneity range of the YFe 12− x Ga x ternary line compound is between ( 1.5 ≤ x ≤ 9.75 ).
