Published online by Cambridge University Press: 26 February 2011
The high temperature strength of new Co-Al-W based alloys consisting of a ?-Co (fcc) matrix phase and a high volume fraction of ?'-Co3(Al, W) ternary L12 intermetallic compound has been examined in order to understand the strengthening mechanisms and to explore the possibility for high temperature applications. The flow stress exhibits a strong, positive dependence on temperature above 873 K. Additions of Ta improve the high temperature strength, and the strength of a Ta containing alloy is comparable to Ni-base superalloys at 1173 K. Transmission microscopy on the deformed Ta containing alloy revealed that the active slip modes within the ?' precipitates are <110>{111} and <112>{111} below and above the peak temperature, respectively. At the peak flow temperature, multiple slip modes including <110>{111}, <110>{001} and <112>{111} were observed.