Depinning transition for a screw dislocation in a model solid solution

TL;DR

This study combines atomistic simulations and statistical theory to analyze the depinning transition of screw dislocations in Ni(Al) solid solutions, revealing that screw dislocations exhibit similar pinning behavior to edge dislocations due to core structure effects.

Contribution

It provides the first atomic-level demonstration that screw dislocations in Ni(Al) have critical shear stress comparable to edge dislocations, challenging classical assumptions.

Findings

Screw dislocation pinning stress is similar to edge dislocation stress.

Dislocation core structure influences pinning behavior.

Statistical theory predicts simulation results across Al concentrations.

Abstract

On the basis of the classical dislocation theory, the Solid Solution Hardening (SSH) is commonly ascribed to the pinning of the edge dislocations. At the atomic level, the theoretical study of the dislocation cores contrasts with such a prediction. Using the static molecular simulations with some interatomic effective potentials, we demonstrate numerically that the critical resolved shear stress associated to a screw dislocation in a random Ni(Al) single crystal has same order as the edge one. Such a result is imposed by the details of the dislocation stacking fault and the core dissociation into Shockley partials. The SSH statistical theory is employed to tentatively predict analytically the data acquired through our atomistic simulations at different Al concentration.