Study on Helium Bubble Coalescence in the Slip Plane of Titanium

Helium bubble growth and coalescence in the slip plane as well as the influence on substrate were studied using the molecular dynamics method. In the slip plane, the helium bubbles grow first along the slip plane and then grow toward the side which is short one atomic layer in the form of a hexagonal structure at low temperature. The growth rates of helium bubbles are related to the addition rate of helium atoms and their surrounding environments. After coalescence, the coalesced helium bubble grows first toward the side that is short one atomic layer. Then it grows along the slip plane with a velocity less than the growth rate before coalescence. Helium bubble growth and coalescence in the slip plane have significant influence on the substrate. During the process, the preexisting slipping metal atoms are pushed back to the normal lattice sites, and the crystal structure of the metal is recovered around the helium bubbles. The recovered area changes with the number of helium atoms in the bubble and the temperature of the substrate. The simulation results indicate that the preexisting grain boundary is beneficial for enhancing the helium damage resistance of metal.