Influence of the loading system stiffness on the jerky flow in Al-Mg alloy at inelastic and postcritical deformation stages

Abstract

The work is devoted to studying the issues of experimental studies of the behavior of materials under conditions of inhomogeneous discontinuous flow at the stages of plastic and supercritical deformation (deformation softening). Obtaining reliable experimental data on the indicated stages of inelastic deformation of materials is important for understanding the physical processes occurring in materials during deformation and ultimately leading to fracture. The results of tests are presented, confirming the influence of the rigidity of the loading system in relation to the working part of the sample on the processes of intermittent plastic deformation. The tests were carried out on samples of Al-Mg alloy. The loading rigidity was varied using a rig with variable rigidity. Registration of displacement and deformation fields on the surface of the working part of the samples was carried out by a non-contact video system Vic-3D Correlated Solutions based on the digital image correlation (DIC) technique. The use of this system makes it possible to measure both deformation at the macro level and the distribution of its components in the working part of the specimen under conditions of inhomogeneous discontinuous deformation. As a result of tensile tests, deformation diagrams were obtained for Al-Mg alloy samples tested at different values ​​of the rigidity of the loading system: 120 MN/m (nominal value), 50 MN/m, 18 MN/m, and 5 MN/m. All the diagrams show discontinuous plastic deformation (the Portevin-Le Chatelier effect). A decrease in the rigidity of loading with respect to the working part of the specimen led to a change in the type of discontinuous yield and an increase in the magnitude of the stress drop at each tooth of the diagram. The indicated effects of inhomogeneous plastic deformation are observed both at the stage of strain hardening and at the stage of postcritical deformation.