Helium behavior in alpha-particle irradiated copper under thermal annealing

Copper specimens were preirradiated by α-particles (50 eV, 0.3-3,6·1021 m-2) through the special filter-mask and subjected to following thermal treatment at temperatures up to 0.95Tmelt for 1-100 h. The helium behavior in the materials was investigated by the method of scanning electron microscopy and profile measurement of a surface. Migration of helium bubbles in the field of stress gradient caused the nucleation and growth of the long-distance gas-filled cracks. It is shown, that development of helium bubbles in a closed bulk of the specimens during high-temperature annealing leads to appearing steps on irradiated surface followed by flacks and blisters. (author)