Isothermal cross section of the cobalt-nickel-tantalum ternary system at 1000 deg C

Studied is the character of phase equilibriums in the cobalt-nickel-tantalum system. An isothermal system cross section is plotted at 1000 deg. NiTa and CoTa compounds form a continuous series of solid solutions in a system. NiTa2 and CoTa2 compounds are isomorphous and the solubility of Co in NiTa2 and Ni in CoTa2 does not exceed 10 at.%. Three-phase fields occupy the most part of an isothermal cross section. Alloy microstructure permits to determine the number of phases being in an equilibrium. Alloy microhardness measurement confirms a solid solution formation between TaCo and TaNi compounds, its absence in case of Ta2Co and Ta2Ni, and also permits to specify Ta solubility boundary in Co-Ni solid solution. Presented are characteristics of intermetallic compounds formed in Ni-Ta and Co-Ta double systems