Abnormal densification of dislocation networks during creep deformation in a single crystal superalloy with a small γ / γ ′ lattice misfit

Generally, with a large lattice misfit, dislocations tend to move smoothly via cross-slip in gamma channels, and rapidly reorient themselves from the (110 ) to (100 ) direction on the surface of gamma ' ' cuboids to form complete networks in single-crystal superalloys. However, in this study, dense and complete dislocation networks also formed in a single-crystal superalloy with a small gamma/gamma ' ' lattice misfit during high-temperature creep deformation. The abnormal densification of dislocation networks was proven to be related to the anomalous enrichment of W and Ta in gamma ' ' phases during the secondary creep stage. Microstructural analysis suggested that anomalous enrichment contributed to an elevated antiphase boundary energy (APBE) of gamma ' ' phases and led to more vacancies within the gamma phase, promoting dislocation climb. The higher APBE of gamma ' ' phases impeded dislocations from cutting into gamma ' ' phases, providing enough time for interfacial dislocations to climb through vacancies and rotate to form dense dislocation networks.