A 6061 aluminum alloy target sleeve from the high flux isotope reactor, originally in a precipitation-hardened condition, was examined for neutron radiation damage after exposure to a maximum fast fluence of 9.2 × 10²² n/cm² (E > 0.1 MeV) and a thermal fluence of 1.38 × 10²³ n/cm² at 60 C (140 F). Voids and a transmutation-produced silicon precipitate were found to cause about 1.1 percent internal swelling; a surface oxide scale contributed additional swelling. Irradiation-induced strength increases were measured at test temperatures in the range 25 to 200 C (77 to 392 F) and are accounted for in terms of the observed silicon precipitate and an associated dislocation structure. There was also a loss of ductility that was most severe at 200 C. The fracture mode appeared to remain transgranular over the range of test temperatures.