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

Abstract

Generally, with a large lattice misfit, dislocations tend to move smoothly via cross-slip in γ channels, and rapidly reorient themselves from the 〈110〉 to 〈100〉 direction on the surface of γ′ 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 γ/γ′ 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 γ′ phases during the secondary creep stage. Microstructural analysis suggested that anomalous enrichment contributed to an elevated antiphase boundary energy (APBE) of γ′ phases and led to more vacancies within the γ phase, promoting dislocation climb. The higher APBE of γ′ phases impeded dislocations from cutting into γ′ phases, providing enough time for interfacial dislocations to climb through vacancies and rotate to form dense dislocation networks.