Abstract:The phase equilibria in Co-rich region of Co−Ti−Ta system were studied. The microstructure and XRD analysis together with EDS determination show that L1₂ type Co₃Ti phase and Laves_C36_Co₃Ta phase get equilibrium with α-Co phase from 1 000 to 1 200 °C. The Co₃Ti phase possesses a solubility of Ta higher than 10%, and the addition of Ta stabilizes the Co₃Ti phase. The isothermal sections of the Co−Ti−Ta system in the Co-rich region at 1 000, 1 100 and 1 200 °C were constructed according to the result.

Key words: L1₂ type intermetallic compound; phase equilibrium; Co−Ti−Ta; Co-based superalloys