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

The gamma' solvus temperature is essential for high temperature microstructural stability and strengthening of the newly developed Co-AI-W-base alloys, but few were above 1100 degrees C since their discovery. In the current study, two experimental alloys containing both Ti and Ta were reported to have high gamma' solvus temperatures of 1131 and 1157 degrees C, respectively. Typical gamma/gamma' two-phase microstructure with high volume fraction of gamma' precipitates presented after aging at high temperature above 1100 degrees C in two experimental alloys. Furthermore, the gamma/gamma' microstructure still remained with a gamma' volume fraction about 63% and no formation of secondary phase at 1050 degrees C for 1000 h. This work indicates the promising microstructural stability to further develop this class of Co-base alloys. (C) 2013 Elsevier B.V. All rights reserved.