On stress assisted dislocation constriction and cross-slip

A novel semidiscrete Peierls–Nabarro model is introduced which can be used to study dislocation spreading at more than one slip plane, such as dislocation cross-slip and junctions. The strength of the model, when combined with an atomistic simulation for dislocation core properties, is without suffering from the uncertainties associated with empirical potentials. Therefore, this method is particularly useful in providing insight into alloy design when empirical potentials are not available or not reliable for such multi-element systems. The model is applied to study the external stress assisted dislocation cross-slip and constriction process in two fcc metals, Al and Ag, exhibiting different deformation properties. We find that the screw dislocation in Al can cross-slip spontaneously in contrast with that in Ag, where the screw dislocation splits into two partials that cannot cross-slip without first being constricted. The dislocation response to an external stress is examined in detail. The dislocation constriction energy and the critical stress for cross-slip are determined, and from the latter, we estimate the cross-slip energy barrier for straight screw dislocations.