Defect interactions and formation of nanometer γ phases within γ' precipitates in Ni-Co-based superalloys during creep

Interactions between different stacking faults (SFs) and microtwins (MTs) in gamma' precipitates within Ni-Co-based superalloys during creep were investigated with atomic resolution. And significant segregation of Co and Cr was detected at SF-SF, SF-MT and MT-MT intersections in gamma' precipitates within samples crept at intermediate temperatures (680-750 degrees C) under different stresses. Local concentration of gamma' formers (Al and Ti) were decreased below 10 at.% which is too low to stabilize chemically ordered gamma' phase at such intersections. Localized trans-formation from chemically ordered gamma' to disordered gamma was confirmed by atomic-resolution imaging. Quantitative analyses indicated that pipe diffusion along interfacial dislocations should play an important role in facilitating localized gamma'-to-gamma transformation. Formation of gamma nanorods/nanoplates along those intersections within gamma' pre-cipitates can impede glide of twinning dislocations and superlattice dislocations, which can consequently play a role in resisting creep deformation of the alloy.

Automated summary

Interactions between different stacking faults (SFs) and microtwins (MTs) in gamma' precipitates within Ni-Co-based superalloys during creep were investigated. Significant segregation of Co and Cr was detected at SF-SF, SF-MT and MT-MT intersections. Local concentration of gamma' formers (Al and Ti) were decreased below 10 at.%, leading to localized transformation from chemically ordered gamma' to disordered gamma. Formation of gamma nanorods/nanoplates impeded twinning dislocations and superlattice dislocations, resisting creep deformation of the alloy.