Multi-scale modeling of dislocation-precipitate interactions in Fe: from molecular dynamics to discrete dislocations

TL;DR

This paper integrates molecular dynamics and discrete dislocation dynamics to model how precipitates influence dislocation motion in iron, providing insights into the microscopic mechanisms affecting material strength.

Contribution

It introduces a multi-scale modeling approach combining MD and DDD to study dislocation-precipitate interactions in BCC iron, with parameters derived from MD simulations.

Findings

Dislocation-precipitate interactions are effectively modeled using Gaussian potentials.

Critical unpinning stresses are comparable between MD and DDD simulations.

The study elucidates pinning and depinning mechanisms affecting plastic deformation.

Abstract

The stress-driven motion of dislocations in crystalline solids, and thus the ensuing plastic deformation process, is greatly influenced by the presence or absence of various point-like defects such as precipitates or solute atoms. These defects act as obstacles for dislocation motion and hence affect the mechanical properties of the material. Here we combine molecular dynamics studies with three-dimensional discrete dislocation dynamics simulations in order to model the interaction between different kinds of precipitates and a $\frac{1}{2}\langle 1 1 1\rangle$ $\{1 1 0\}$ edge dislocation in BCC iron. We have implemented immobile spherical precipitates into the ParaDis discrete dislocation dynamics code, with the dislocations interacting with the precipitates via a Gaussian potential, generating a normal force acting on the dislocation segments. The parameters used in the discrete dislocation dynamics simulations for the precipitate potential, the dislocation mobility, shear modulus and dislocation core energy are obtained from molecular dynamics simulations. We compare the critical stresses needed to unpin the dislocation from the precipitate in molecular dynamics and discrete dislocation dynamics simulations in order to fit the two methods together, and discuss the variety of the relevant pinning/depinning mechanisms.