Explanation of the discrepancy between the measured and atomistically calculated yield stresses in body-centered cubic metals

TL;DR

This paper introduces a mesoscopic model explaining why measured yield stresses in BCC metals are 2-3 times lower than atomistic Peierls stress calculations, highlighting dislocation interactions as key factors.

Contribution

A novel mesoscopic model that accounts for dislocation interactions to explain yield stress discrepancies in BCC metals.

Findings

Dislocation interactions reduce the effective yield stress by a factor of two to three.

The model aligns with experimental measurements of yield stresses at low temperatures.

Mutual dislocation interactions are crucial in understanding plastic deformation in BCC metals.

Abstract

We propose a mesoscopic model that explains the factor of two to three discrepancy between experimentally measured yield stresses of BCC metals at low temperatures and typical Peierls stresses determined by atomistic simulations of isolated screw dislocations. The model involves a Frank-Read type source emitting dislocations that become pure screws at a certain distance from the source and, owing to their high Peierls stress, control its operation. However, due to the mutual interaction between emitted dislocations the group consisting of both non-screw and screw dislocations can move at an applied stress that is about a factor of two to three lower than the stress needed for the glide of individual screw dislocations.