Nonlinear dynamics of an individual Portevin--Le Chatelier deformation bands

Abstract

Based on high-speed studies of the dynamics of Portevin--Le Chatelier ambryo bands with a temporal resolution of up to 20 μs and a spatial resolution of up to 10 μm/px, their classification is proposed, which includes four types of bands depending on the nature of interaction with other bands and the sample surface (using the example of a polycrystalline aluminum-magnesium alloy). It has been found that all types of ambryo bands demonstrate nonlinear dynamics with a sharp acceleration of the band tip and the growth rate of its volume at the final stage before reaching the sample surface. A phenomenological model of the nonlinear growth of the ambryo band is proposed, which explains the exponential self-acceleration stage observed experimentally. The sharp absorption of acoustic noise at the stage of accelerated band growth is discussed. Keywords: nonlinear dynamics, Portevin--Le Chatelier effect, deformation ambryo bands, acoustic emission, dislocation mobility, aluminum-magnesium alloy.