Phase Equilibria at 1173 K in the Ternary Fe-Pt-Tb System

The solid-state phase equilibria in the ternary Fe-Pt-Tb system in the compositional region below 75 at.%Tb at 1173 K have been studied by using x-ray diffraction, scanning electron microscopy and energy dispersion spectroscopy techniques. The 1173 K isothermal section consists of 18 single-phase regions, 33 two-phase regions, and 16 three-phase regions. At 1173 K, the maximum solid solubility of Pt in α-(Fe, Tb) is less than 2 at.%Pt and that of Pt in Fe 2 Tb, Fe 3 Tb, Fe 23 Tb 6 , Fe 17 Tb 2 is below 1 at.%Pt; the compounds Pt 5 Tb, Pt 3 Tb, Pt 2 Tb, Pt 4 Tb 3 , PtTb, Pt 4 Tb 5 , Pt 3 Tb 5 , PtTb 2 , and PtTb 3 are confirmed to exist at 1173 K and the highest solid solubility of Fe in them is below 1 at.% Fe; the maximum solid solubility of Tb in α-(Fe, Pt), γ-(Fe, Pt), FePt, FePt 3 , and (Pt, Fe) (namely, the solid solution of Fe in Pt) is about 1, 2, 1.9, 1.5, and 1.5 at.%Tb, respectively. No ternary compound was found to exist in this section at 1173 K.