Activated states for cross-slip at screw dislocation intersections in face-centered cubic nickel and copper via atomistic simulation

SI Rao and DM Dimiduk and JA El-Awady and TA Parthasarathy and MD Uchic and C Woodward, ACTA MATERIALIA, 58, 5547-5557 (2010).

DOI: 10.1016/j.actamat.2010.06.005

We extend our recent simulation studies where a screw dislocation in face-centered cubic (fcc) Ni was found to spontaneously attain a low energy partially cross-slipped configuration upon intersecting a forest dislocation. Using atomistic (molecular statics) simulations with embedded atom potentials, we evaluated the activation barrier for a dislocation to transform from fully residing on the glide plane to fully residing on a cross-slip plane intersecting a forest dislocation in both Ni and Cu. The activation energies were obtained by determining equilibrium configurations (energies) when variable pure tensile or compressive stresses were applied along the 1 1 1 direction on the partially cross-slipped state. We show that the activation energy is a factor of 2-5 lower than that for cross-slip in isolation via the Escaig process. The cross-slip activation energies obtained at the intersection in Cu were in reasonable accord with the experimentally determined cross-slip activation energy for Cu. Further, the activation barrier for cross-slip at these intersections was shown to be linearly proportional to (d/b)ln(root 3d/b)(1/2), as in the Escaig process, where d is the Shockley partial dislocation spacing and b is the Burgers vector of the screw dislocation. These results suggest that cross-slip should be preferentially observed at selected screw dislocation intersections in fcc materials. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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