MECHANISMS OF SWELLING SUPPRESSION IN COLD-WORKED PHOSPHORUS-MODIFIED FE-NI-CR ALLOYS

Three cold-worked phosphorous-modified Fe-15Ni-13Cr-base alloys were irradiated with simultaneous Fe- and He-ion beams to doses of about lOOdpa at a helium implantation rate of 20at.p.p.m./dpa. The three alloys correspond to compositions that led to increasing densities of a very fine phosphide precipitate. In the case of the alloy with the highest precipitate density, the swelling was suppressed to the greatest extent. The results are interpreted in terms of the theory of cavity swelling, which provides the central concept of a critical radius and critical number of gas atoms required for cavity swelling. The large interfacial area of the needle-shaped phosphide precipitates led to profuse bubble nucleation at the interface. The high density of bubbles slowed the accumulation of gas atoms in individual bubbles and thus delayed the onset of point-defect-driven cavity swelling. After interpreting the present data in terms of these concepts, more general features of cavity swelling reduction by an increase in cavity number density are explored. The varying ce:degrees of swelling observed in a wide variety of experiments, described in the literature, becomes systematic when the present concepts are applied. © 1990 Taylor & Francis Group, LLC.