Line tension model of the interaction between dislocations and extended obstacles to glide

Within the framework of the line tension model, the “force-distance” relation is calculated for dislocations cutting extended obstacles to their glide. The treatment is based on the determination of the Gibbs free energy of activation Δ G, and includes consideration of “chemical” terms which refer to the creation of structural disorder, line energy terms which refer to the changing lengths of the dislocation inside and outside the particle and the work done by the applied effective stress $\text{ɹ}{}^{\mathrm{*}}$. The activation volume is obtained from the relation υ = −∂ΔG/∂τ^*. It turns out to be the absolute value of the Burgers vector multiplied by the total area swept by the dislocation in the particle and in the matrix during the activation event. In this paper an attempt is made to clarify the concept of the “activation distance” for extended obstacles, which in the literature is either ignored or treated incorrectly. Some examples are calculated for a rhomboidal cutting plane and different types of interaction.