Evolution of superdislocation structures of 6% Re/5% Ru single-crystal nickel-based alloys under high-temperature creep conditions

Abstract The evolution of superdislocation structures during the creep of a single-crystal alloy was investigated through creep performance testing, microstructural observations, and comparative analysis of dislocation configurations. The results revealed that, in the early stage of creep, dislocations activated in the γ phase first glide along the {111} plane and subsequently reach the {100} γ / γ ′ interface. At this interface, they transform into 〈110〉 60° mixed dislocations, which gradually develop into a 〈110〉 dislocation network. As creep deformation proceeds, these 〈110〉 60° mixed dislocations progressively convert into 〈100〉 type dislocations at the γ / γ ′ {100} interface via a specific climb mechanism driven by mismatch stress, eventually forming a 〈100〉 dislocation network. During the middle and late stages of creep, dislocations begin to shear the rafted γ ′ phase sequentially, first single dislocations, then anti-phase boundary (APB) plus dislocation pairs, and finally superlattice intrinsic stacking faults (SISFs) plus partial dislocation. Consequently, the strain-softening mechanism during creep is governed not only by the increased density of specific superdislocations but also by the continuous evolution and interaction of multiple dislocation types.