Phase equilibria of the Co–Ta–Ti system at 950 °C

The phase equilibria of the Co–Ta–Ti system at 950 °C were investigated via a combination of diffusion couples and equilibrated alloys. The samples were examined by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The experimental results showed the existence of no ternary compounds at 950 °C. Two continuous series of solid solutions form between γ-TaCo2 and TiCo2 (h), and between β-TaCo2 and TiCo2 (c), respectively. The 950 °C isothermal section consists of 10 single-phase regions, 15 binary phase regions and 6 ternary phase regions. The following six three-phase equilibria at 950 °C were well determined: (1) (Co) + TiCo3 + Ta2Co7, (2) TiCo3 + Ta2Co7 + (Ta,Ti)Co2 (h), (3) (Ta,Ti)Co2 (c) + TiCo + TaCo, (4) TiCo + TaCo + Ta2Co, (5) TiCo + Ta2Co + (Ta,Ti) and (6) TiCo + Ti2Co + (Ta,Ti).