Threshold stresses for dislocation climb over hard particles: The effect of an attractive interaction

We present a model for the effect of an attractive interaction between dislocations and hard spherical particles on the process of dislocation bypass by local climb. The interaction is treated by assigning a line tension to the dislocation which is lower in the vicinity of the particle than in the matrix. We find that even for very modest interactions, the strongest barrier to dislocation bypass is no longer provided by the climb obstacle, but rather by the detachment of the dislocation from the particle after climb over the particle is complete. The model provides a possible explanation for some experimentally observed dislocation configurations in crept ODS superalloys and for the creep thresholds which are typical of such alloys.