Abstract: On the basis of Au-Ag, Au-Dy and Ag-Dy binary phase diagrams, the 700℃ isothermal section of Au-Ag-Dy ternary system(Dy≤35%, mole fraction) was established by X-ray diffraction analysis, differential thermal analysis and optical microscopy. It is found that there is a long single-phase region, Au(Ag) or Ag(Au), along the Au-Ag binary isomorphous system on the gold-silver-rich side of the 700℃ isothermal section and between the binary compound Au₂Dy and Ag₂Dy there is the all proportional solid solution, (Au₂Dy) or (Ag₂Dy). It is confirmed that the partial 700℃ isothermal section consists of six single-phase regions: solid solution Au(Ag) or Ag(Au), (Au2Dy) or (Ag₂Dy), Au₆Dy, Au₅₁Dy₁₄, Au₃Dy and Ag₅₁Dy₁₄; nine binary-phase regions: (Au₂Dy)+Au(Ag), Au₆Dy+Au(Ag), Au(Ag)+Ag₅₁Dy₁₄, Ag₅₁Dy₁₄+(Au₂Dy), Au₃Dy+(Au₂Dy), Au₃Dy+Au₅₁Dy₁₄, Au₅₁Dy₁₄+Au₆Dy, Au₅₁Dy₁₄+Au(Ag) and Au(Ag)+Au₃Dy; four ternary regions: Ag₅₁Dy₁₄+(Au₂Dy)+Au(Ag), (Au₂Dy)+Au(Ag)+Au₃Dy, Au(Ag)+Au₃Dy+Au₅₁Dy₁₄ and Au₅₁Dy₁₄+Au(Ag)+Au₆Dy. No new ternary compound is formed in the gold-silver-rich field(Dy≤35%) of the Au-Ag-Dy ternary system.

Key words: Au-Ag-Dy ternary system; phase diagram; isothermal section