Flow stress anomalies in γ/γ′ two-phase Co–Al–W-base alloys

The high-temperature strength of new cobalt-base alloys reinforced with a high volume fraction of a Co3(Al, W) ternary L12 intermetallic compound has been examined. The flow stress exhibits a strong, positive dependence on temperature above 873 K and the strength of a Co–Al–W–Ta quaternary alloy is comparable to that of nickel-base superalloys at 1173 K. The flow anomaly is attributed to the activation of multiple slip modes within the precipitates. Above the peak flow temperature, 〈1 1 2〉 dislocation shearing of precipitates is the dominant deformation mode.