A molecular dynamics study of helium bubble formation and gas release near titanium surfaces

Helium bubble formation and gas release near titanium surfaces have been studied using molecular dynamics. The results show that the formation of helium bubbles near a titanium surface is accompanied by the production of defects and the drift of defects toward the metal surfaces as well as an increase in the number of surface metal atoms. It is also shown that the helium bubbles burst at the mechanical stability limit of the metal. The metal surface morphology is modified by the bursting of the helium bubbles, with an increase in the surface roughness and the formation of surface pores as well as the re-deposition of the helium atoms. In contrast, the subsurface metal will retain its perfect crystal structure. The size of the resultant surface pore depends on the initial bubble diameter. For a small bubble, the pore can be healed by the thermal evolution of the substrate.