The interaction between vacancies and the ½〈111〉 {11¯0} edge dislocation in body centred cubic metals

Abstract

The interactions between vacancies and the ½〈111〉 {11¯0} edge dislocation have been studied using real space computer simulation techniques and a series of interatomic potentials representing α-iron. Since a prerequisite to such a study is a thorough knowledge of the structure of the dislocation, the relevant details are presented using the differential displacement mapping and Burgers vector distribution methods. The dislocation is shown to have a planar core structure and a Burgers vector which is split into a series of ‘fractional’ components. The predominant interaction mechanism for vacancies near the dislocation core region is of the second order inhomogeneity or induced type. Thus, the interactions are attractive for vacancy locations both above and below the dislocation slip plane. Also, for the potentials used, the simulations show that the maximum vacancy-dislocation binding energy is approximately one half of the vacancy formation energy. For certain vacancy sites, the forces which exist between the two defects can cause the dislocation to move in its slip plane in the sense which increases the binding energy. The vacancy positions for which this behaviour occurs are correlated with the locations of the fractional components of the Burgers vector into which the dislocation core is split.