New insights into the microstructures and mechanical responses of large- scale colliding aluminum nanospheres

B Ma and HD Zeng and XL Cheng and CY Zhang and ZP Lu, COMPUTATIONAL MATERIALS SCIENCE, 163, 167-175 (2019).

DOI: 10.1016/j.commatsci.2019.03.031

Aluminum nanospheres are served as a promising solid propellant, but the dynamic responses of their impact-induced agglomerations are not fully understood. For this reason, ReaxFF-molecular dynamics simulations were performed to investigate in detail the microstructures and mechanical behaviors of large-scale colliding aluminum nanospheres with diameter 10 nm at three impact velocity scenarios over the range of 200-2000 m/s. In terms of the microstructural evolutions of all considered systems, two aluminum nanospheres were adhered to each other but their directional deformations varied with the impact velocity. According to the stress- strain curves analyses, aluminum nanospheres underwent an important mechanical process of elastic deformation transiting to plastic deformation along with the increase in the impact velocity. Interestingly, we found that the impact-dependent elastic-plastic deformation gave rise to the structural transition of fcc to hcp by using the common neighbor analysis method. It most favors the hcp phase embryo nucleation while the impact velocity was 1200 m/s, and the fraction of hcp atoms reaches up to 40% under such condition. Moreover, the atomic mechanism of local fcc-hcp transition was revealed in this study, providing a quantitatively understanding of the phase transition process for controllable dynamical mechanical characteristics of large- scale colliding aluminum nanospheres.

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