Dislocation avalanches are rapid discreet events during plastic deformation, in which defects are reorganized collectively. This intermittent flow behavior has been observed in microcrystals, whereas macroscopic plasticity appears as a smooth process. Intermittent plastic flow has been observed in several different systems. In AlMg Alloys, interaction between solute and dislocations can cause sudden jump during dynamic strain aging.In metallic glass, it can be observed via shear banding with stress localization and single crystal plasticity, it shows up as slip burst.However, analysis of the events with orders-magnitude difference in sizes with different crystallographic structure reveals power-law scaling between the number of events and their magnitude, or scale-free flow.
This microscopic instability of plasticity can have profound consequences on mechanical behavior of microcrystals. The increased relative size of the fluctuations makes it difficult to control the plastic forming process. Moreover, at small specimen sizes the yield stress is not well defined by the 0.2% plastic strain criterion anymore, since this value varies specimen by specimen.
Similar intermittent effects has been studied in many completely different systems, including intermittency of energy dissipation in magnetism (Barkhausen effect), superconductivity, earthquakes, and friction.
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