Elemental segregation-dependent γ″ nucleation on stacking faults during creep in 718Plus superalloy

In this study, we investigate the segregation behavior and interactions of stacking faults(SFs) and microtwins in the 718Plus under 650 °C/800 MPa and 730 °C/500 MPa by atomic-scale Z-contrast (High angle annular dark field image, HAADF) in combination with creep models. Our results reveal that creep deformation is dominated by SFs and microtwins, with pronounced Nb and Co enrichment alongside Al and Ni depletion at SFs sites. Furthermore, γ″-Ni₃Nb precipitates nucleate preferentially at SFs intersections, suggesting a dynamic interplay between defect evolution and precipitation. A comparative analysis of microtwinning-based creep models and experimental data demonstrates that microtwinning in the γ' phase provides the dominant strengthening contribution, yielding a slip resistance of approximately 92.3 MPa-accounting for 62% of the total hardening. In stark contrast, γ″-induced hardening is negligible (∼0.15 MPa). These atomic-scale insights advance our understanding of creep mechanisms and γ″ precipitation in 718Plus superalloys, providing critical guidance for alloy design.