The study of mechanism of localized shear fracture in AlMg6 alloy under dynamic loading on a split Hopkinson pressure bar

This work is devoted to the substantiation of one of the mechanisms of plastic strain localization under conditions of high-rate dynamic loading associated with jump-like processes in the defect structure of materials. The specimen behavior under dynamic loading was investigated using a split Hopkinson pressure bar. In order to identify the characteristic stages of strain localization, we performed in-situ thermodynamical studies of the deformation process by recording temperature fields with the CEDIP Silver 450M high-speed infrared camera. The temperature measurements made in the zone of strain localization do not support the wide-spread idea that the strain localization mechanism is caused by thermoplastic instability. Dynamic tests were carried out for specimens, which were specially designed to study plastic strain localization in AlMg6 alloy under conditions of dynamic loading on the split Hopkinson pressure bar using the StrainMaster strain measurement system. The specimens after the experiment were subjected to microstructural analysis using an optical interferometer-profile meter and a scanning electron microscope. The structural analysis revealed the correlated behavior of defect ensembles, which can be classified as a structural transition facilitating strain localization. Experimental data, examination of deformed specimen structure and data of numerical simulation with consideration for kinetics of microdefect accumulation in the material allow us to infer that one of the mechanisms of plastic strain localization at high loading rates is caused by jump-like processes in the defect ensembles.