Effects of Dose Rate on the Precipitate Distribution in an Ion-Irradiated Nickel-Aluminum Alloy

The present experiments were performed to investigate the effect of a factor of 100 difference in damage dose rate on /gamma/sub p/rime/-precipitates in Ni-6.84Al. Prior to irradiation, the alloy was solution-treated and aged to produce /gamma/sub p/rime/-precipitates with a mean cube edge of 33.7 nm. Specimens were examined by transmission electron microscopy following irradiation with 2.8 MeV/sup 58/Ni/sup +/ ions to peak damage doses of 0.81, 2.5 and 8.1 displacements per atom (dpa) at an irradiation temperature of 725 degree C for damage dose rates of 4.4 X 10/sup -4/ dpa/s. Analysis of the observed behavior by exisitng theories in the literature indicated that all of the effects noted could not be explained by any single, currently available theory. Satisfactory agreement was found with a treatment based on a combination of several previously proposed growth, dissolution, and reprecipitation mechanisms.