Improved high temperature γ′ stability of Co-Al-W-base alloys containing Ti and Ta

The γ′ solvus temperature is essential for high temperature microstructural stability and strengthening of the newly developed Co-Al-W-base alloys, but few were above 1100 °C since their discovery. In the current study, two experimental alloys containing both Ti and Ta were reported to have high γ′ solvus temperatures of 1131 and 1157 °C, respectively. Typical γ/γ′ two-phase microstructure with high volume fraction of γ′ precipitates presented after aging at high temperature above 1100 °C in two experimental alloys. Furthermore, the γ/γ′ microstructure still remained with a γ′ volume fraction about 63% and no formation of secondary phase at 1050 °C for 1000 h. This work indicates the promising microstructural stability to further develop this class of Co-base alloys.