Activated State for Cross-Slip at Screw Dislocation Intersections in Face-Centered Cubic Nickel

摘要

We extend our recent work where a screw dislocation in 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 evaluate the activation barrier for a dislocation to transform from fully residing on the glide plane to fully residing on the cross-slip plane intersecting a forest dislocation. The activation energies were obtained by determining equilibrium configurations (energies) when variable pure tensile or compressive stresses are applied along the direction on the partially cross-slipped state. We show that the activation energy is a factor of 3 - 6 lower than that for cross slip in isolation via the Escaig process. Further, the activation barrier for cross- slip at these intersections is shown to be linearly proportional to (d/b)ln(d/b), 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.