Coupling Between Ductile Damage Evolution and Phase Transition in Single Crystal Niobium Subjected to High Strain Rate Loading

The primary objective of this work is to investigate the dynamic damage behavior of single crystal niobium at high strain rate from the atomic perspective. Molecular dynamics simulations are conducted to characterize the void evolution combined with the plastic deformation and phase transition. Interestingly, the reversal phenomenon of the body-centered cubic structure occurring in the late stage of the progressive damage process is caused by the change in potential energy. A large quantity of hexagonal closet packed (HCP) structures are found to be stacked around the voids, demonstrating that the void nucleation is beneficial to the formation of the HCP phase. Importantly, 900 K is considered as characteristic temperature for dominating the phase transition behavior. When the temperature is below 900 K, the face-centered cubic (FCC) phase appears, followed by the HCP phase with continuous loading. However, when T ≥ 900 K, the HCP phase is firstly observed and subsequently the FCC phase appears in the system. Besides, it is detectable that the void nucleation precedes the dislocation, which is explained by the fact that the dislocation emission is dependent upon void size. An increase in temperature is beneficial to dislocation movement. Accordingly, there is a strong sensitivity of dynamic performance to temperature in BCC-based niobium.