Spontaneous athermal cross-slip nucleation at screw dislocation intersections in FCC metals and L1₂ intermetallics investigated via atomistic simulations

Abstract

In this manuscript, we extend on our prior work to show that under certain conditions cross-slip nucleation is athermal and spontaneous with zero activation energy in FCC elemental metals such as Ni and Cu, and L1₂ intermetallic compounds such as Ni₃Al. Using atomistic simulations (molecular statics), we show that spontaneous cross-slip occurs at mildly repulsive intersections. Further, the local Shockley partial dislocation interactions at such repulsive intersections are found to be attractive leading to junction formation. The line orientation of the intersecting dislocation determines whether the spontaneous cross-slip nucleation occurs from either the glide plane to the cross-slip plane or vice versa. Collectively, these results suggest that cross-slip should be preferentially observed at selected screw dislocation intersections in FCC-derviative metals and alloys.

Keywords:

• cross-slip
• dislocation intersections
• atomistic simulations
• nickel
• copper

Acknowledgements

The authors acknowledge use of the 3d molecular dynamics code, LAMMPS, which was developed at Sandia National Laboratory by Dr Steve Plimpton and co-workers. This work was supported by AFOSR (Dr David Stargel), and by a grant of computer time from the DOD High Performance Computing Modernization Program, at the Aeronautical Systems Center/Major Shared Resource Center. The work was performed at the US Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright–Patterson AFB. JAE acknowledges support by DARPA Grant # N66001-12-1-4229.