PSI - Issue 79

Volodymyr Hutsaylyuk et al. / Procedia Structural Integrity 79 (2026) 501–507

505

TEM observations (Figure 4) revealed the formation of subgrain cells and microchannels of plastic flow with low-angle boundaries, consistent with substructure rearrangement rather than full recrystallization. These changes correlate directly with the enhanced plasticity and energy dissipation observed during testing. The obtained results can be interpreted through the concept of defect self-organization under non-stationary stress fields. When a short force impulse is superimposed on monotonic loading, the resulting non-equilibrium conditions cause a rapid redistribution of dislocations, local stress relaxation, and the initiation of additional slip systems. These processes lead to the formation of banded substructures, subgrain refinement, and enhanced ductility without a significant loss of strength. The timing of impulse application is crucial. When the impulse is applied before or near the yield point, the dislocation structure is still relatively mobile and easily reconfigures, enabling activation of multiple slip systems. This leads to more uniform plastic flow, delayed localization, and increased elongation. When the impulse is applied after yielding, the structure has already developed a more stable deformation pattern, and the capacity for further reconfiguration is lower, resulting in a weaker effect on plasticity. This behavior aligns with published findings on subgrain evolution in Al–Cu alloys under dynamic loading— accelerated defect rearrangement and formation of low-angle boundaries. The observed lamellar-to-banded transition and presence of flow channels are characteristic signatures of such non-equilibrium defect organization. From a practical standpoint, this mechanism has important implications for fatigue resistance. A stabilized subgrain structure can delay strain localization and crack initiation. Therefore, controlled non-stationary loading may serve as a microstructural engineering tool to extend the service life of aerospace components.

Fig. 4. TEM observations: a, b) microchannel and subgrain observations; c, d) confirmation of self-organization processes.

Fig. 5. Forms of grains on the surface of the plate of the 2024-T3 aluminum alloy sample: a) combined loading; b) monotonic tension.