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The effects of dislocation climb on plastic deformation during loading and
unloading are studied using a two-dimensional discrete dislocation dynamics
model. Simulations are performed for polycrystalline thin films passivated on
both surfaces. Dislocation climb lowers the overall level of the stress inside
thin films and reduces the work hardening rate. Climb decreases the density of
dislocations in pile-ups and reduces back stresses. These factors result in a
smaller Bauschinger effect on unloading compared to simulations without climb.
As dislocations continue to climb at the onset of unloading and the dislocation
density continues to increase, the initial unloading slope increases with
decreasing unloading rate. Because climb disperses dislocations, fewer
dislocations are annihilated during unloading, leading to a higher dislocation
density at the end of the unloading step.