Dynamic impact constitutive relation of 6008-T6 aluminum alloy based on dislocation density and second-phase particle strengthening effects

To investigate the mechanical properties and constitutive relationship of 6008-T6 aluminum alloy under dynamic impact loading, dynamic impact and microscopic experiments were conducted on 6008-T6 aluminum alloy. The results demonstrated that 6008-T6 aluminum alloy exhibits strain hardening effects. As the loading strain rates increased, the grains became more refined, whereas the dislocation density and number of second-phase particles (mainly Mg₂Si) increased. Several dislocations interacted with each other, thereby preventing further dislocation movement and improving the material's strength. The precipitation of second-phase particles impeded the motion of dislocations and increased the flow stress of the material. A constitutive model of dynamic impacts was developed based on the evolution of dislocation density and reinforcing effects of second-phase particles. Furthermore, based on the isotropic assumption, the damage evolution equation of 6008-T6 aluminum alloy was obtained by introducing the energy release rate. By combining the dynamic constitutive model of materials under dynamic impact compression conditions, the dynamic constitutive model of materials was obtained under dynamic impact tensile conditions. Moreover, the rationality of the model was confirmed by comparing the model's data with experimental data. In this study, we examined the macro mechanical response, microstructure, and dynamic mechanical behavior of the 6008-T6 aluminum alloy under dynamic impact conditions, which can serve as a theoretical basis and analytical tool for the structural design and safety evaluation of high-speed trains.