A. E. Zolotov

Nucleation mechanisms of macrolocalized deformation bands

For the first time, a phenomenological classification of the nucleation mechanisms of bands of macrolocalized deformation is formulated that is based on data from the high speed optical monitoring of a surface of aluminum-magnezium alloy deformed with a uniformly growing rate of applied stress,

Electromagnetic emission in the development of macroscopically unstable plastic deformation of a metal

\dot \sigma _0 = const

Direct current induced suppression of the Portevin-Le Chatelier serrated deformation in the aluminum-magnesium alloy 5056

. The classification includes eight nucleation mechanisms that depend on the applied stress: from the initial stage of formation of the Lüders band to the periodical nucleation of the conjugative bands in the structure of a neck prior to sample rupturing. The role of different mechanisms of band nucleation in the general picture of the jerky deformation of a metal is discussed.

Study of the Mechanisms of Current-Induced Suppression of Serrated Deformation

The nonlinear dynamics of the space-time structure of macrolocalized deformation is studied by a set of high-speed in situ methods under the conditions of serrated creep in an aluminum-magnesium Al-6 wt % Mg alloy at room temperature. Macroscopic deformation jumps with an amplitude of several percent are detected in the creep curve of this alloy. It is found that a complex space-time structure of macrolocalized deformation bands moving in a correlated manner forms spontaneously in the material during the development of a deformation jump. The difference between the observed picture of deformation bands and the well-known Portevin-Le Chatelier classification of deformation bands is discussed.

Spectral and dynamic analysis of plastic instabilities during serrated creep of the aluminum-magnesium alloy

Electromagnetic emission accompanying the serrated deformation of the aluminum‒magnesium alloy Al-6Mg has been revealed and studied experimentally. By means of high-speed video recording and a complex of methods for measuring the strain, load, and electric potential, it has been found that there is a relation between the electromagnetic emission signals and the dynamics of deformation bands. Possible mechanisms of the generation of electromagnetic signals have been discussed.

Investigation of the effect of electric current on serrated deformation and acoustic emission in the aluminum-magnesium alloy 5056

The dynamics and morphology of macrolocalized deformation bands have been investigated using a complex of high-speed in situ methods under the conditions of serrated creep of flat samples of the aluminum-magnesium alloy 5456 with different aspect ratios. It has been found that, at the front of a macroscopic plastic deformation jump, a complex structure of propagating deformation bands, which are considered as macrolocalized deformation “quanta,” is spontaneously formed in the material. It has been shown that, with an increase in the sample length, the deformation behavior of the alloy tends to the state of self-organized criticality.

Dynamics of a Lüders Band and Destruction of an Aluminum-Magnesium Alloy, Initiated by a Stress Concentrator

The effect of direct current induced suppression of the Portevin-Le Chatelier serrated deformation in the aluminum-magnesium alloy 5056 has been revealed experimentally. This effect manifests itself as an increase in the critical plastic strain, which precedes the onset of serrations in the stress-strain curve, with an increase in the current density in the range from 15 to 60 A/mm2. It has been shown that the observed effect is not related to the Joule heating of the entire specimen. Possible mechanisms of the phenomenon have been discussed.

Effect of an aggressive medium on discontinuous deformation of aluminum–magnesium alloy AlMg6

The main results of studying the influence of electric current on the Portevin‒Le Chatelier serrated deformation in some commercial aluminum alloys of the Al‒Mg, Al‒Li-Mg, Al‒Zn‒Mg‒Cu, and Al‒Cu systems are reported. It is found that the passage of a low-density (~10–60 A/mm2) dc current leads to the suppression of serrated deformation and band formation in all alloys under study, except for the Al‒Cu alloy. Possible mechanisms of this phenomenon are discussed, basically in terms of possible influence of current on the processes of precipitation and dynamic strain aging, which are used to explain the Portevin‒Le Chatelier effect.