Study of localized shear failure of AMg6 alloy specimens under static and dynamic loading

Experiments on dynamic loading of specimens made of AMg6 alloy were conducted on the Hopkinson-Kolsky bar apparatus, while the static loading tests were carried out on the Testometric electromechanical testing machine. Temperature fields generated in the processes of dynamic deformation were investigated "in-situ" by recording temperatures with a high-speed infrared camera CEDIP Silver 450M. The temperature measured in the zone of strain localization formed in the material during dynamic loading does not confirm the traditional view of the strain localization mechanism as the one associated with thermoplastic instability. Static and dynamic tests were carried out for AMg6 alloy specimens specifically designed to study plastic strain localization using for this purpose the Testometric electromechanical testing machine and split Gopkinson-Kolsky bar, as well as the StrainMaster system for noninvasive measurement of shape and strains. Displacement and strain fields generated in specially shaped AMg6 alloy specimens under static deformation and dynamic loading were constructed. Comparison of the temperature fields experimentally obtained under dynamic loading and strain fields under static and dynamic loading with the results of numerical modeling made with account of kinetics of mesodefect accumulation in the material shows good agreement to the accuracy of ~20%. After the experiments, the surface relief of specially shaped stressed specimens was examined using an optical interferometer-profile meter New View-5010. The processing of the obtained 3D strain relief data made it possible to evaluate the scale invariant (Hurst index) and spatial scale of the area where the correlated behavior of mesodefects was observed. The data of experimental studies, the examination of the surface topography of deformed specimens, structural studies, as well as the data of numerical simulation conducted with consideration of the kinetics of mesodefect accumulation in the material suggest that one of the mechanisms of plastic strain localization in the alloy AMg6 at the examined rates of loading is associated with discontinuous processes in the defect structure of materials. However, the character of specimen failure under static and dynamic loading is due to realization of different scenarios for the behavior of defective subsystems.