Multiscale modeling of plastic deformation of molybdenum and tungsten: III. Effects of temperature and plastic strain rate

TL;DR

This paper links atomic-level dislocation glide modeling at 0 K with thermally activated motion, incorporating temperature and strain rate effects through a hypothetical Peierls barrier and transition state theory.

Contribution

It introduces a novel Peierls barrier concept that accounts for complex stress responses and models temperature and strain rate effects on dislocation motion.

Findings

Developed a stress-dependent Peierls barrier model.

Linked atomic dislocation behavior with macroscopic yield stress.

Provided a framework for predicting temperature and strain rate effects.

Abstract

In this paper we develop a link between the atomic-level modeling of the glide of 1/2<111> screw dislocations at 0 K and the thermally activated motion of these dislocations via nucleation of pairs of kinks. For this purpose, we introduce the concept of a hypothetical Peierls barrier, which reproduces all the aspects of the dislocation glide at 0 K resulting from the complex response to non-glide stresses and is expressed in a compact form by the yield criteria advanced in Part II. To achieve this the barrier is dependent not only on the crystal symmetry and interatomic bonding but also on the applied stress tensor. Standard models are then employed to evaluate the activation enthalpy of kink-pairs formation, which is now also a function of the full applied stress tensor. The transition states theory links then this mechanism with the temperature and strain rate dependence of the yield stress.