Статистические закономерности развития локализации деформации при пластическом течении в сплаве АМг6

Abstract

The laws governing the development of localization of plastic deformation under the conditions of manifestation of the effect of space-time heterogeneity (the Portevin-Le Chatelier effect) were investigated. Compression tests were carried out on cylindrical specimens of the aluminum alloy AMg6 with a constant strain rate of 0.4 –1.7 ·10 − 1 s−1, inclined by 2° from the vertical. This shape of the specimens determines a preferential direction for the formation of slip bands that allows for achieving large strains (up to 80 %) without failure. Calorimetric studies of samples of the AMg6 alloy with varying degrees of deformation were carried out using a STA “Jupiter” 449 calorimeter. Statistical distributions of the intervals between the plastic flow stress fluctuations were analyzed and two critical points were found that indicate a change in the mechanisms of plastic deformation. The transition through the first critical point corresponds to the formation of multiple regions of localized plasticity. The further plastic flow of the studied alloy reveals multiscale signs of localization of plastic deformation over the rest of the plastic flow curve. At the stage of developed plastic flow, the maximum level of stored energy is observed during deformation. The transition through the second critical point is associated with the formation of nuclei of macroscopic failure, which is accompanied by the release of the stored strain energy and a decrease in calorimetric effects. The form of the probability density function of the intervals between the plastic flow stress fluctuations and the probability density function of the flow stress fluctuations confirm the self-similar nature of multiscale correlations of these quantities, similar to that observed for a closed turbulent flow of fluids between two rotating disks in the Karman experiment with large Reynolds numbers.