Microstructural Evolution Mechanism of Al-Based Nano-Powders under Impact Loading

With the continuous improvement of the material performance requirements of the charged warheads, elucidating the microstructural evolution of nano-powders under shock loading becomes critical for optimizing damage-element materials. In this study, molecular dynamics simulations were employed to comparatively investigate the shock wave propagation characteristics, phase transition behavior, and dislocation evolution of typical Al-based nanostructured powders Al-Fe-Ni and Al-Fe. This study reveals the mechanisms of impact velocity and Ni element on the evolution of Al-based nanoparticles. The results indicate that increasing shock velocity significantly enhances the thermodynamic response of the materials and promotes phase transition. Fe and Ni particles exhibit minimal deformation at an impact velocity of 0.6 km/s. When the velocity was increased to 1.5 km/s, the pressure exceeds 35 GPa and the temperature surpasses 6000 K, resulting in the melting of Al particles and deep fusion of Fe and Ni particles. The thermodynamic coupling effects lead to the formation of a large number of other structures. Furthermore, shock velocity does not affect the spatial distribution of dislocations but significantly regulates dislocation density. The introduction of the Ni element enhances the thermodynamic response of the material, alters the evolution pathway of the body-centered cubic phase and increases the proportion of hexagonal close-packed structures. Moreover, Ni element introduction raises the dislocation density, adjusts the timing of dislocation reactions, and promotes the formation of sessile dislocations, dislocation pinning, and dislocation loop structures, thereby influencing the temporal evolution and spatial characteristics of dislocations. These findings provide a theoretical basis for optimizing the processing of damage-element materials and their application.