The formation and migration of He bubbles in a Fe-17Ni-16Cr austenitic model alloy at 400 to 1250C were studied by means of in situ electron microscopy, energy dispersive spectrometry and EELS analysis. The nucleation of bubbles under 10keV He+ ion bombardment predominated at 400C, while growth predominated above 600C. It was found that the mean square of the migration distance was proportional to time, and yielded diffusivities which ranged from 10-18 to 10-20m2/s at 1185C; depending upon the diameter (1 to 3nm). The results suggested that the mobility of He-vacancy complexes or bubbles was an important factor which governed the formation of He bubbles.

Formation and Migration of Helium Bubbles in Fe-16Cr-17Ni Austenitic Alloy at High Temperature. K.Ono, K.Arakawa, M.Ohashi, H.Kurata, K.Hojou, N.Yoshida: Journal of Nuclear Materials, 2000, 283-287, 210-4