Nickel-Ion Damage in a Precipitation-Hardened Nickel-Aluminum

A precipitation-hardened nickel 14 atom percent aluminum alloy has been irradiated with 2.8 MeV ⁵⁸Ni⁺ ions at a damage rate of 4.4 × 10^-2 displacements per atom (dpa)/s, over a temperature range of 525 to 725 °C (977 to 1337 °F), to a damage level of 20 dpa, and at 625 °C (1157°F) over a dose range of 4 to 125 dpa. The experiment was designed to examine the stability of Ni₃Al precipitates as a function of temperature and dose as well as their role in reducing swelling.

Prior to irradiation, the precipitates were cuboidal in shape with a mean edge length of 400 Å. Ion bombardment to 20 dpa at 725 °C (1337 °F) generated a higher precipitate density with a reduced and highly uniform size of 85 Å. At all other temperatures, the precipitate structures were less well defined and took on a ragged appearance with a wide spread in sizes as small precipitates formed between the original ones. A few scattered voids were formed at the two highest damage levels at 625 °C (1157 °F), but the swelling was negligible.