Experimental Determination of the Isothermal Sections and Liquidus Surface Projection of the Co–V–Zr System

The construction of the experimental liquidus surface projection and isothermal sections of the Co–V–Zr ternary system was based on the analyses of solidification microstructures and phase constituents. A new compound τ with Cr_0.5Fe_1.5Zr-type was identified, and the measured composition range of Zr in τ was ∼ 28.6 to 57.3 at. pct and 32.9 to 56.8 at. pct at 1100 °C and 1000 °C, respectively. The liquidus surface projection identified nine primary solidification areas, while two primary solidification areas were inferred from binary diagrams. Moreover, eight and ten three-phase equilibria were determined at 1100 °C and 1000 °C, respectively. The measured solubility of V in Co₂₃Zr₆, Co₂Zr and CoZr reached ~ 0.5, 7.6 and 4.1 at. pct at 1100 °C. Meanwhile, the solubility of V in Co₂₃Zr₆, Co₂Zr, CoZr and CoZr₂ was measured to be ~ 0.4, 7.6, 1.6 and 3.6 at. pct at 1000 °C. The solubility of Zr in Co₂V₃ was ~ 3.6 at. pct at 1100 °C, while the solubility of Zr in Co₃V, Co₂V₃ and CoV₃ was determined ~ 1.3, 3.0 and 4.5 at. pct at 1000 °C, respectively. The experimental data can help improve the thermodynamic parameters of the Co–V–Zr system and advance the development of databases for multi-component Co-based superalloys.