Non-linear jog-dragging effect on the mobility law of edge dislocations in face-centered cubic nickel

Abstract

Dislocation jogs have strong effects on dislocation motion that governs the strain-hardening behavior of crystalline solids, but how to properly account for their effect in mesoscale models remains poorly understood. We develop a mobility model for jogged edge dislocations in FCC nickel, based on systematic molecular dynamics (MD) simulations across a range of jog configurations, stresses, and temperatures. At low stresses, jogged edge dislocations exhibit non-linear, thermally activated dragging and a higher Peierls barrier compared to straight dislocations. Surprisingly, stress-velocity curves for a given jog configuration across varying temperatures intersect at an invariant point ($\tau_{\rm c}$, $v_{\rm c}$), where $\tau_{\rm c}$ delineates thermally-activated and phonon-drag regimes and is close to the Peierls stress ($\tau_{\rm p}$). Motivated by this observation, we propose a simple three-section expression for jogged dislocation mobility, featuring minimal and physically interpretable parameters. This mobility law offers a realistic description of jog effects for dislocation dynamics (DD) simulations, improving their physical fidelity for crystal plasticity predictions.