Dynamic Response of Nanoscale He Bubbles in Single Crystal Al during Release from a High-Pressure State

Previous researches have presented some knowledge about the shock loading and unloading of the nanoscale He bubble. However, the He bubble will undergo a long high-pressure adiabatic relaxation process after being shocked. This work focuses on the release path of the nanoscale He bubble in single crystal Al from a stable high-pressure state by molecular dynamics method. Firstly, we consider the case that two opposite release waves meet at the center of the He bubble. Combined with the analysis of deformation mechanism and stress waveform around the He bubble, the difference of evolution law of He bubble under different pressure conditions is revealed. The evolution of the number and distribution of voids with or without the He bubble is compared. And the nucleation region gradually extends to both sides of the He bubble with the increase of initial Hugoniot pressure. Moreover, when a single unloading wave is considered to sweep through the He bubble, the microjet formation in the He bubble is found due to the pressure gradient effect. The shape and velocity distribution of internal and surface jets are discussed.