Small-scale plasticity: Insights into dislocation avalanche velocities

We report direct measurements of displacement jump velocities in deforming nano- and microcrystals. These velocities exhibit large scatter and no correlation with plastic strain, crystal size or applied stress. Statistical analysis for the displacement jump velocities shows a cubic power-law decay, with a shoulder at low velocities. Our results indicate that the collective motion of dislocations in the deforming crystals is dominated by statistical fluctuations within the internal stresses, rather than by a mobility law that depends on the externally applied stress.