Dislocation self-organization processes and crystal plasticity

Abstract

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Current pattern of plastic deformation stages

“…The nature of changing the stages upon active plastic deformation was discussed in a number of works in which authors focused their attention on different aspects of this phenomenon [20]. Among these aspects are: 1) changes in the slip character (from the planar to spatial slip) and hence in the shift zone size, 2) changes in the number of acting slip systems, 3) transition from simple dislocation accumulation to reorganization of the dislocation structure and increase in the fraction of annihilating dislocations, 4) actuation of rotational deformation modes implying the development of persistent and discrete misorientations, and 5) substructural transformations, that is, transformations of one substructure into another and different mechanisms of dislocation deceleration associated with them.…”

Wave correlation of elementary deformation events during plastic deformation of metals

“…This means that the acoustic emission spectrum is provided by a secondary effect in relation to the primary acoustic signal. According to our publications, the primary source of acoustic emission is the exit of a dislocation ensemble of the slip system to the surface and formation of a single band of deformation [8].…”

“…In this state, plastic flow of the crystal lattice is due to a weak local stability (or the loss of stability) relative to the shift in the range of stress concentrators [3], when the movement of the dislocation segment through the above-barrier is athermal. Localization of the low-stability (or unstable) state of the crystal structure by plastic deformation is usually associated with the process of self-organization of dislocations, which is manifested in the formation of lines and slip bands [8]. The evolution of the structure of acoustic emission signals reflects selforganization processes characterized by a weak stability (or instability) and elementary processes in the atomic subsystem under external influence [9].…”

Low-stabilty states of aluminum crystal lattice and acoustic emission under high-temperature straining

“…These experiments suggest that structural levels of different scales are involved into process of deformation: from micro-to meso-and macroscale level. Localization of the low-stability state under plastic deformation for a classical three-stage σ -ε dependence (here σ is mechanical stress and ε is relative strain) is attributed to an interaction of dislocations and their self-organization [18]. An inclusion of self-organization into consideration allows drawing a fundamental conclusion that the experimentally observed multiple deformation behavior and a variety of dislocation structures result from the evolution of the dislocation ensemble via collective and cooperative phenomena and their spatial arrangement made manifest as the formation of slip lines and bands [18].…”