Peierls potential of screw dislocations in bcc transition metals: Predictions from density functional theory

Abstract

It is well known that screw dislocation motion dominates the plastic deformation in body-centeredcubic metals at low temperatures. The nature of the non-planar structure of screw dislocations gives rise to high lattice friction which results in strong temperature and strain rate dependence of plastic flow. Thus, the nature of the Peierls potential, which is responsible for the high lattice resistance, is an important physical property of the material. However, current empirical potentials give a complicated picture of the Peierls potential. Here, we investigate the nature of the Peierls potential using Density Functional Theory in the BCC transition metals. The results show that the shape of the Peierls potential is sinusoidal for every material investigated. Furthermore, we show the magintiude of the potential scales strongly with the energy per-unit-length of the screw dislocation in the material.

Hydrogen embrittlement I. Analysis of hydrogen-enhanced localized plasticity: Effect of hydrogen on the velocity of screw dislocations inα-Fe

“…Fully discrete simulations using empirical potentials also have been used to model the interaction of hydrogen with dislocations but the predictive power of these studies is to a great extent limited by the reliability of the interatomic potential [10]. On the other hand, first-principles calculations are mostly limited to studies of bulk phases, point defects, simple grain boundaries, and dislocation core structures [11,12].…”

“…DFT results show that the 1 2 [111] screw dislocation core in α-Fe is nondegenerate and spreads onto the three {110} planes [11,12]. This nonplanar core structure significantly affects screw dislocation mobility.…”

Dislocation locking versus easy glide in titanium and zirconium

“…4a that the energy pathway, which corresponds to −2 ≤ ζ ≤ 0, has a high energy barrier (11.4 meV Å −1 ). Therefore, the glide of a dislocation in its pyramidal spreading plane is subjected to a high lattice friction, of the same order as in bcc metals 25,26 , where dislocation glide is thermally activated up to room temperature and requires the nucleation and propagation of kink pairs along the dislocation lines. Another potential glide mechanism is that the dislocation first cross-slips into a prismatic plane-that is, changes its spreading plane from pyramidal to prismatic-and then glides in the prismatic plane.…”

{110} Slip with {112} slip traces in bcc Tungsten

“…Many particular aspects of the deformation characteristics in bcc metals are ascribed to the 3-dimensional core structure of screw dislocations, which is consequently anchored in the lattice910. Most of the details on the core structure of screw and on the slip mechanisms are obtained from atomistic simulations41112131415 revealing aspects such as the role of stresses other than the resolved shear stress that break the symmetry of the core structure16 or the role of other particular orientations corresponding with a high Peierls stress17. These new aspects form important input for higher-lengthscale models such as discrete dislocation simulation models used to investigate the yield and plastic behavior of a bcc single crystal171819202122.…”