Formation and strength of dislocation junctions in FCC metals: A study by dislocation dynamics and atomistic simulations

The structure and strength of three-dimensional Lomer-Cottrell junctions ar e studied using four different models. These models represent increasing le vels of sophistication, with each case including some new physical effect. The line tension approximation makes use only of the elastic self energy of the dislocation lines. The edge-screw dislocation dynamics model increases the sophistication by including the elastic interactions between all of th e dislocation segments. At the next level of sophistication, the nodal disl ocation dynamics method accounts for the dissociation of the core into part ial dislocations. Finally, the quasicontinuum method takes into account the core effects at the atomic level. The results show that although the line tension model represents a huge simplification of the physics of dislocatio ns, it is able to reproduce the equilibrium structure of any type of Lomer- Cottrell interaction, both in the absence and presence of an externally app lied stress. The pseudo-analytical description can thus be used as a bench mark for the development of dislocation dynamics simulations.