A New Approach to Strength Prediction of Ni-Base Disk Superalloys with Dual-Phase γ/γ′

Previously reported strength prediction models for polycrystalline Ni-base superalloys tend to underestimate the overall strength. This is primarily due to neglecting the rule of mixtures for hardening by γ/γ′ and inaccurate estimation of other strengthening factors such as solid solution hardening of γ matrix and grain boundary strengthening. To address these issues, a series of single-crystal tie-line modeling alloys with γ′ size suitable for validating the strong pair-coupling and Orowan looping mechanisms were prepared, in an attempt to develop more reliable γ′ hardening models. Critical resolved shear stress values were measured on these modeling alloys at 650 °C using compression tests, which allowed the distinction between strength contribution from rule of mixture and interfacial strength. Compared with the experimentally obtained interfacial strengths, the predicted results by classical models could not reflect the strength increment expected at higher γ′ volume fraction. Hence, a modified version of the classical equations has been proposed here for improved predictability.