Dislocation avalanches: Role of temperature, grain size and strain hardening

Previous acoustic emission experiments on creeping single crystals of ice showed that the dynamics of an assembly of interacting dislocations self-organized into a scale-free pattern characterized by power law distributions of avalanche sizes. In this paper, we investigate the possible incidence of temperature and microstructure on this emerging pattern. Temperature does not modify the nature of the critical dynamics. However, it seems to modify the avalanche's relaxation owing to dislocation-phonon interactions. On the other hand, tests on polycrystals reveal the role of grain boundaries as barriers to dislocation motion hindering the emergence of the scale-free pattern, as well as the role of kinematic hardening as a polarized internal stress. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.