  Jerky flow in solids results from collective dynamics of dislocations which
gives rise to serrated deformation curves and a complex evolution of the strain
heterogeneity. A rich example of this phenomenon is the Portevin-Le Chatelier
effect in alloys. The corresponding spatiotemporal patterns showed some
universal features which provided a basis for a well-known phenomenological
classification. Recent studies revealed peculiar features in both the stress
serration sequences and the kinematics of deformation bands in Al-based alloys
containing fine microstructure elements, such as nanosize precipitates and (or)
submicron grains. In the present work, jerky flow of an AlMgScZr alloy is
studied using statistical analysis of stress serrations and the accompanying
acoustic emission. As in the case of coarse-grained binary AlMg alloys, the
amplitude distributions of acoustic events obey a power-law scaling which is
usually considered as evidence of avalanchelike dynamics. However, the scaling
exponents display specific dependences on the strain and strain rate for the
investigated materials. The observed effects bear evidence to a competition
between the phenomena of synchronization and randomization of dislocation
avalanches, which may shed light on the mechanisms leading to a high variety of
jerky flow patterns observed in applied alloys.
