| Ya.V. Konakov, | I.A. Ovid'ko | , A.G. Sheinerman and N.V. Skiba |
| A model is suggested that describes collective migration of two neighboring low-angle tilt boundaries in nanocrystalline metals under fatigue loading. Within the model, low-angle tilt boundaries are considered as the walls of edge lattice dislocations, while the triple junctions that terminate these boundaries contain wedge disclinations that accommodate the stress fields created by the dislocation walls. The simulation using the method of two-dimensional dislocation dynamics for the case of nanocrystalline Fe, revealed various migration modes of tilt boundaries under fatigue loading. These include the reversible migration of tilt boundaries, their split as well as their motion to adjacent high-angle grain boundaries and subsequent coalescence with these boundaries. The simulations demonstrate that the mode of boundary migration is determined by the level of the applied load and explain the recent observations of the reversible grain lattice reorientation near a crack tip in a nanocrystalline Ni-Fe alloy under fatigue loading. |
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