Effect of mechanical deformation on development of helium porosity

The formation of helium bubbles in 18–10 steel and 20–45 nickel alloy implanted by He ions during tension is studied, and helium release from them during high-temperature deformation is analyzed. During helium implantation, an applied tensile stress favors bubble formation and material swelling. Annealing and deformation of the irradiated materials increase the bubble size. Helium bubble migration and accumulation at grain boundaries cause cracking. Bubble migration is caused by a stress gradient. The deformation of the irradiated materials leads to an increase in the release rate of accumulated helium. A model is proposed for the development of helium porosity in a material under stress. A brittle fracture criterion is formulated for such a material.