Simulation of the interaction between two different 1/2 screw dislocations in body-centered-cubic metal niobium

Abstract

Dislocation-dislocation interaction plays important roles in the strain hardening of crystalline materials. In this work, Molecular statics (MS) and dynamics (MD) simulations have been carried out to investigate the interaction of a screw-screw model which contains two non-parallel, non-coplanar 1/2<111> screw dislocations in niobium single crystal with body-centered-cubic structure. By means of MS simulations, we investigated the relationship between the dislocation spacing and the external shear stress needed to intersect them, and found the result is quite close to that derivated on the basis of dislocation elasticity theory. Using MD simulations, we studied the interaction of the interactive model and found that the evolution of the dislocation configurations under the applied stress is as follows: the intersection of the two dislocations, reaction to form a [001] binary junction, formation of the edge dipole and final release of the two dislocations. Depending on whether the local cross-slip of the screw segment takes place, the dislocation with an edge dipole connected by the [001] junction may be depinned by pinching off a 1/2[111] dislocation loop or not. Analogous release processes have been established theoretically or deduced experimentally. In addition, the effect of temperature and strain-rate on the interaction process is presented.