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M: Metallphysik

M V: HV V

M V.1: Invited Talk

Thursday, March 29, 2001, 14:30–15:00, S5.3

Scaling and Criticality in Plastic Deformation — •Michael Zaiser — Max-Planck Institut für Metallforschung, Heisenbergstr.1, D-70569 Stuttgart, Germany

Plastic deformation of crystalline solids is governed by collective motions of large numbers of interacting dislocations under the influence of an externally applied stress. On microscopic and mesoscopic scales, plastic flow exhibits an intermittent dynamics which proceeds in discrete ’avalanches’. This is manifest both in the motion of individual dislocations (unzipping of obstacles) and in the collective motion of interacting dislocation lines. It is argued that such behaviour may be considered in terms of the close-to-critical dynamics of a slowly driven complex system, and it is discussed to which extent theoretical results obtained in this field during the last decade may contribute to our understanding of crystal plasticity. As examples, we discuss power-law scaling observed in transient creep and low-frequency internal friction, dislocation avalanches monitored by acoustic emission, and TEM observations of fractal dislocation networks.