Vertical sections of Tb0.15Ho0.85Fey-Tb0.3Dy0.7Fey (y=1.85, 1.9, 2.0) in Tb-Dy-Ho-Fe system

Abstract

The x(Tb0.15Ho0.85Fey)+(1–x)(Tb0.3Dy0.7Fey) (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9; y=1.85, 1.9, 2.0) samples were prepared by a vacuum arc furnace, and annealed at 1000 °C for 1 d and at 950 °C for a week. Three vertical sections of Tb0.15Ho0.85Fey-Tb0.3Dy0.7Fey (y=1.85, 1.9, 2.0) in the Tb-Dy-Ho-Fe system were determined using optical microscopy, scanning electron microscopy, energy dispersion X-ray spectroscopy, X-ray diffraction, and differential thermal analysis. These vertical sections consisted of two single-phase regions: L and (Tb,Dy,Ho)Fe2; four two-phase regions: L+(Tb,Dy,Ho)Fe3, L+(Tb,Dy,Ho)Fe2, (Tb,Dy,Ho)Fe2+(Tb,Dy,Ho)Fe3, and (Tb,Dy,Ho)Fe2+(Tb,Dy,Ho). The high Ho content of (Tb,Dy,Ho)Fey alloys led to the elevation of the peritectic temperature of L+(Tb,Dy,Ho)Fe3→(Tb,Dy,Ho)Fe2. The region of (Tb,Dy,Ho)Fe2 phase was shifted towards the side of rich-Ho with the Fe content increasing. It meant that the substitution of Ho for Dy or Tb had a marked effect on the solidification process of (Tb,Dy,Ho)Fe2 compounds.