Atomistic simulations of cross-slip nucleation at screw dislocation intersections in face-centered cubic nickel

摘要

The Escaig model for thermally activated cross-slip in face-centered cubic (fcc) materials assumes that cross-slip preferentially occurs at obstacles that produce large stress gradients on the Shockley partials of the screw dislocations. However, it is unclear as to the source, identity and concentration of such obstacles in single-phase fcc materials. Embedded atom potential, molecular-statics simulations of screw character dislocation intersections with 120 forest dislocations in fcc Ni are described that illustrate a mechanism for cross-slip nucleation. The simulations show how such intersections readily produce cross-slip nuclei and thus may be preferential sites for cross-slip. The energies of the dislocation intersection cores are estimated and it is shown that a partially cross-slipped configuration for the intersection is the most stable. In addition, simple threedimensional dislocation dynamics simulations accounting for Shockley partials are shown to qualitatively reproduce the atomistically determined core structures for the same dislocation intersections.