Effect of Preliminary Combined Loading on the Failure Micromechanisms of Aluminum Alloy 2024-T351

This paper presents the results of research on the effect of preliminary combined loading—comprising monotonic tension and an additional force impulse—on the failure micromechanisms of aluminium alloy 2024-T351. The aim was to understand the mechanisms responsible for changes in the mechanical properties of the material under the influence of dynamic non-equilibrium processes and to identify the structural consequences of this type of loading. The impulse applied during monotonic deformation leads to the formation of a new type of structural organisation—the so-called dissipative structure. It results from local transformations aimed at restoring energetic equilibrium in the material. This organisation develops simultaneously at multiple scale levels, from macro to micro, and causes localised modifications in mechanical properties. Fractographic analysis revealed significant differences in fracture surface morphology between samples subjected only to monotonic tension and those exposed to combined loading. Transmission electron microscopy (TEM) confirmed the formation of microbands and subgrains as a result of relaxation processes. These features indicate self-organisation of defects and local hydrodynamic flow channels, explaining the observed increase in plasticity after combined loading. The study confirms a strong correlation between failure micromechanisms and the intensity and character of preloading. The findings provide a physical basis for modelling the interaction between impulse loading, strain localisation, and structural evolution.