Abstract
The {111} antiphase-boundary (APB) energies Γ of the L12 long-range-ordered γ′ phases that precipitation strengthen the commercial nickel-based superalloys Nimonic PE16 and Nimonic 105 were measured by three independent methods. Γ was derived, firstly, from the dependence of the critical resolved shear stress on the dispersion of the γ′ precipitates in these superalloys, secondly, from the minimum size of Orowan dislocation loops which can be sustained by γ′ precipitates and, thirdly, from the separations of the superpartial dislocations bounding APB faults in the single-phase γ′ alloys. The latter method is based on state-of-the-art transmission electron microscopy investigations and is considered as the most direct. The results determined by the three different methods show (with one exception) satisfactory agreement. This proves the validity of all three experimental approaches and thus supports the theoretical models on which the first two methods are based. Since Γ governs the strength of superalloys, this parameter is of utmost importance.