Quantitative analysis of the yield behavior of a 〈1 1 1〉/2 screw dislocation in α-iron

Abstract

In previous work, bond-order potentials (BOPs) have been used to establish a general yield criterion, different from the Schmid law, for the glide of 〈1 1 1〉/2 screw dislocations on {1 1 0} planes in body-centered cubic metals, while their applications are restricted to the 2D simulations at 0 K because of their low computational efficiency. On the other hand, embedded-atom-method (EAM) potentials have been generally employed for long dislocation segments at finite temperatures, but there is no study to clarify whether or not they can reproduce the yield criteria revealed by the BOPs. In this work, systematic atomistic simulations with an EAM potential have been performed to calculate the behaviors of 〈1 1 1〉/2 screw dislocations in α-iron under different loading conditions. We find that at 0 K, the simulation results can be well explained by the general yield criterion when the glide is restricted to {1 1 0} planes. Under uniaxial loadings, the activated slip systems are consistent with the experimental observations. At finite temperatures, as a preliminary attempt, the influence of the non-glide stress on the slip planes is presented, which could not be rationalized by the yield criterion at 0 K because extra effect from temperatures has come into the picture.