Abstract:Phase equilibria of the Zr-Co-Ge ternary system at 1023, 1173 and 1373 K were precisely measured via alloy sampling associated with electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques. The isothermal sections in the Zr-Co-Ge system were appropriately constructed, containing 29, 28, and 26 three-phase regions at 1023, 1173, and 1373 K, respectively. Except for confirming the five ternary compounds previously reported in the literature, a new ternary phase τ was detected with a remarkable homogeneity range, consisting of 13.8-19.4 at.% Co at 1023 K, 12.9-19.0 at.% Co at 1173 K and 12.3-14.9 at.% Co at 1373 K. And, an invariant reaction was deduced to occur at a temperature between 1023 and 1173 K, i.e., τ+τ1 τ4+ZrGe₂. Besides, the third element Ge can partly substitute Co in some Co-Zr intermediate phases, e.g., CoZr₂ and Co₂₃Zr₆ where the maximum solubility of Ge can separately reach up to 22.8 at.% and 20.3 at.%, respectively.

Key words: Zr-Co-Ge ternary system; phase diagram; compound; solubility