The collective behavior of a system of straight parallel dislocations is investigated. It is found by numerical simulation that the internal stress ¢ created by the dislocation has a stochastic component. In order to describe this stochastic character the form of the probability distribution function of the internal stress is determined. It is shown that the mean value of the distribution function is the self-consistent field created by the dislocation and the distribution function decays with 1/£ 3 . ¤ S 0163-1829¥ 98¦ 05230-8 §

Simulation of parallel dynamics of edge dislocations in a 2D hexagonal lattice is carried out on a large scale by means of coarse graining, in the absence of external strain. In order to study the effect of climb on dislocation pattern formation, we allowed (i) isotropic (ii) biased (iii) only glide mobility. Moreover we annihilated dislocations with opposite Burgers vectors close to each other. The main result is that in cases (i) and (ii) cellular structure emerges, for (ii) this happens after a longer transient, while (iii) gives a diffuse looking pattern, similar to former single slip plane simulations. In the course of the evolution of dislocation number and cell size they statistically well satisfy Holt's relation. The cell structure found appears to have a characteristic cell size, in contrast to fractal examples in the presence of mechanical strain. Despite the simplicity of our model, the results are consistent with the recently detected low-density dislocation patterns in melt-grown, non-post-deformed crystals.

During the plastic deformation of crystalline material the dislocations, being the carriers of the plastic flow, tend to form different patterns. Because of the long range nature of dislocation-dislocation interaction, the origin of this self-ordering phenomenon is still an open question. The paper presents a stochastic two-dimensional model derived directly from the properties of individual dislocations making it possible to investigate the problem on a mesoscale. Numerical results obtained in double slip configuration indicate the development of cell structure with fractal character.

International audienceDislocation climb mobilities, assuming vacancy bulk diffusion, are derived and implemented in dislocation dynamics simulations to study the coarsening of vacancy prismatic loops in fcc metals. When loops cannot glide, the comparison of the simulations with a coarsening model based on the line tension approximation shows a good agreement. Dislocation dynamics simulations with both glide and climb are then performed. Allowing for glide of the loops along their prismatic cylinders leads to faster coarsening kinetics, as direct coalescence of the loops is now possible