Shock-induced collapse and migration of nanoscale He bubble in single crystal Al

As a major product of nuclear radiation damage, high-pressure He bubble is a potentially important factor affecting the constitutive response and the damage dynamics of the matrix material. This Letter reports the shock-induced collapse and migration process of He bubble in Al based on atomistic simulations. The He bubble will be compressed to permanent deformation while experiences a finite collapse in comparison with the complete collapse of the voided matrix. Under strong shock, the He bubble can be broken down by the nano-jet of the metal, but it returns to a reduced sphere in the molten metal after long-time evolution, driven by the He-Al interface energy. The Carnhan-Starling hard-sphere model is used to describe the thermodynamics of shocked He bubbles, by establishing the relationship between the diameter of He atom and temperature. In particular, the shock-induced migration of He bubble is revealed, which can be divided into shock acceleration and the following inertial motion. Then, an equation of migration distance related to shock intensity is proposed.