Dislocation interactions in γ-channels between γ′-particles of superalloy single crystals

Abstract

In the present work, a discrete dislocation model (DDM) is used to study interactions of γ-channel dislocations in γ/γ′-microstructures of superalloy single crystals. The study considers three types of γ-channels, 12 (isolated) octahedral face centered cubic slip systems and two macroscopic crystallographic shear-loading conditions. It was found that different types of γ-channels vary with respect to the number of dislocations, which can enter the channels. This effect becomes more important in the presence of misfit stresses. Misfit stresses were integrated into the present analysis by performing preliminary thermoelastic misfit stress calculations, which served as one input for the calculation of the overall stress state. The two other input elements to the overall stress state are the stresses associated with external loading and the dislocation stress fields. The effect of the overall stress state is evaluated considering the Peach–Koehler force, which acts on a central channel dislocation. The results of the study demonstrate that it is not enough to discuss dislocation plasticity in γ/γ′-microstructures merely on the basis of external resolved shear stresses. It was shown that misfit stresses, which attract dislocation loops from one microscopic crystallographic slip system into one type of γ-channel make it more difficult for the same dislocations to enter other γ-channels.