Barrier effect of grain boundaries on the avalanche propagation of polycrystalline plasticity

To investigate the barrier effect of grain boundaries on the propagation of avalanchelike plasticity at the atomic scale, we perform three-dimensional molecular dynamics simulations by using simplified polycrystal models including symmetric-tilt grain boundaries. The cutoffs of the stress-drop distributions following power-law distributions decrease as the size of the crystal grains decreases. We show that some deformation avalanches are confined by grain boundaries; on the other hand, unignorable avalanches penetrate all the grain boundaries included in the models. The blocking probability that one grain boundary hinders this system-spanning avalanche is evaluated by using an elemental probabilistic model.