Collective dynamics of dislocations interacting with mobile solute atoms

Abstract

We study the eect of diusing solute atoms on the collective dynamics of dislocations in plastically deforming crystals, by simulating a twodimensional 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 aected by solute-induced strain hardening in the high-stress regime.

Probing the transition from dislocation jamming to pinning by machine learning

“…where ρ is the total dislocation density and L(r) is approximated by computing the mean line length in spheres of radius r centered at random points along the dislocation structure. We note that in the case of 2D DDD simulations, the average dislocation-dislocation correlation function changed drastically when mobile solutes (pinning points) were introduced to the system [29]. Here we focused on longerrange correlations to avoid possible effects caused by the assigned segment length restrictions of the computations.…”

Effect of transmutation elements Re and Ta on the vacancy formation and dissociation behaviors in W bulk

“…Similar fluctuation in W-Ta system also appeared in others observation. The results suggest that the transmutation elements Re atom has a favored function to form the vacancy, while Ta acts as a delaying role to the vacancy via a solute drag effect [31,32].…”

An efficient implicit time integration method for discrete dislocation dynamics

“…For a short dipole this exactly reproduces Eq. (16). Finally, at a given timestep the Jacobian matrix Ĵ k (according to Eq.…”

“…These are primarily used in cases when the physical consequences of long range dislocation interactions are investigated and when large simulation volumes, large ensembles for statistical averaging, longer timescales and/or higher numerical precision is required. Due to the simplification mentioned above a quantitative agreement with experiments cannot be expected, yet, these tools have been successfully applied to investigate, e.g., creep [15,16], dislocation avalanches [17,18,19] and patterning [20,21] of dislocations. An intermediate class is represented by 2.5D simulations, which are essentially 2D but with the inclusion of some 3D mechanisms, such as dislocation multiplication or dislocation pinning [22,23,24,25,26,27,28].…”