Elevated-temperature heavy-ion damage in (Co 0.78Fe 0.22) 3V ordered alloy

Abstract

Irradiation-induced changes in microstructure were studied in a (Co 0.78Fe 0.22) 3V long-range-ordered alloy after bombardment with 4 MeV nickel ions at temperatures from 843 to 1023 K and damage levels from 10 to 70 dpa. Small cavities and Frank loops were developed, and particles of pre-existing VC phase were redistributed by the irradiation. Long-range order was retained under all irradiation conditions, but domain size was effectively reduced by the Frank loops that served as antiphase boundaries. Simultaneous injection of helium at a rate of 3 at.ppm/dpa and deuterium at a rate of 12 at.ppm/dpa during irradiation produced gas bubbles in the grain boundaries, increased the dislocation and cavity densities, reduced the mean cavity size, but had little effect on the ordered domain size or the redistribution of VC particles. Even with injected gases, swelling remained below 0.25%. It is deduced that swelling did not reach the rapid bias-driven state because the critical cavity size was large.