The Isothermal Section Of The Gd-Dy-Co Ternary System At 800K

The isothermal section of the phase diagram of the Gd-Dy-Co ternary system at 800K was investigated by X-ray powder diffraction (XRD), differential thermal analysis (DTA), optical microscopy and scanning electron microscopy (SEM) techniques. The result shows that this section consists of 9 single-phase regions , 9 two-phase regions and 1 three-phase region. The binary compounds Dy₄Co₃, GdCo₅ and DyCo₅ were not observed at 800K. No ternary compound was found.Nine single-phase regions: a(Co), P((Gd,Dy)₂Co₁7), δ((Gd,Dy)₂Co₇), ε((Gd,Dy)Co₃), η((Gd,Dy)Co₂), θ(Gd₄Co₃), λ(Gd,Dy)₁₂Co-7), μ((Gd, Dy)₃Co),ξ(Gd,Dy).Nine two-phase regions: α+β,β+δ,δ+ε, ε+η, η+θ, η+λ, θ+λ,λ+μ,μ+ξ.One three-phase region: η+θ+λ.Six pairs of corresponding compounds of Gd-Co and Dy-Co, i.e., Gd₂Co₁₇ and Dy₂Co₁₇, Gd₂Co₇ and Dy-2Co₇, GdCo₃ and DyCo₃, GdCo₂ and DyCo₂, Gd₁₂Co₇ and Dy₁₂Co₇, Gd₃Co and Dy₃Co form continuous series pairs of solid solutions. In addition, the single phases a-Gd and a-Dy also form a continuous series of solid solution. The solid solubility of single phases was determined by the disappearing-phase method of the X-ray diffraction analysis. The maximum solid solubility of Dy in Gd₄Co₃ is about 10.8 at. %.