A phenomenological dislocation mobility law for bcc metals

TL;DR

This paper develops a phenomenological dislocation mobility law for bcc metals, validated through simulations and experiments, to better understand temperature-dependent plastic deformation in tungsten micro pillars.

Contribution

It introduces a new generalized dislocation mobility law for bcc metals, integrating theoretical, MD, and experimental insights, and applies it to simulate tungsten micro pillar deformation.

Findings

Model reproduces temperature dependence of flow stress.

Captures shear deformation asymmetries.

Aligns with experimental dislocation microstructures.

Abstract

Dislocation motion in body centered cubic (bcc) metals displays a number of specific features that result in a strong temperature dependence of the flow stress, and in shear deformation asymmetries relative to the loading direction as well as crystal orientation. Here we develop a generalized dislocation mobility law in bcc metals, and demonstrate its use in discrete Dislocation Dynamics (DD) simulations of plastic flow in tungsten (W) micro pillars. We present the theoretical background for dislocation mobility as a motivating basis for the developed law. Analytical theory, molecular dynamics (MD) simulations, and experimental data are used to construct a general phenomenological description. The usefulness of the mobility law is demonstrated through its application to modeling the plastic deformation of W micro pillars. The model is consistent with experimental observations of temperature and orientation dependence of the flow stress and the corresponding dislocation microstructure.