Abstract
The nucleation and growth of helium bubbles in the matrix of ferritic steels has been investigated by ion implantation and subsequent vacuum annealing over a temperature range of 600 - 800 C. Two steels of slightly differing compositions were studied but no significant differences in bubble nucleation and growth were observed. Bubble nucleation, which occurs homogeneously, appears to be more dependent upon the diffusion of vacancies than upon the mobility of helium. Migration and coalescence was found to be the dominant mechanism of growth at all temperatures. Although vacancy collection does occur at the higher temperatures, bubble growth by this mechanism is limited by vacancy source efficiency.