Collective dynamics of dislocations interacting with mobile solute atoms

We study the effect of diffusing solute atoms on the collective dynamics of dislocations in plastically deforming crystals, by simulating a two-dimensional discrete dislocation dynamics model with solute atoms included. We employ various protocols to apply the external stress, including constant, oscillatory and quasistatically increasing stress, and study the resulting dynamics for various values of the solute mobility, temperature, and interaction strength with the dislocations. The values of these parameters dictate if Cottrell clouds are formed around the dislocations, and whether the dislocations are able to drag them along as they move. The relevant solute-induced processes include a temporally increasing average Cottrell cloud size due to cloud merging during the evolution of the dislocation structures subject to constant stresses, and a crossover between a solute-free 'phase' and a regime where solute drag is important for cyclic stresses, controlled by the solute mobility and temperature. Statistics of deformation bursts under quasistatic loading exhibit atypical scaling where the average burst size is directly proportional to its duration, and are also affected by solute-induced strain hardening in the high-stress regime.