Tensile Properties of Neutron-Irradiated 6061 Aluminum Alloy in Annealed and Precipitation-Hardened Conditions

Tension specimens of 6061 aluminum alloy (nominally 1Mg-0.6Si) were heat-treated to give fully annealed (“0” temper) and precipitation-hardened (“T6” temper) conditions, and were irradiated in water at 328 K (0.35 T_m) to fast (>0.1 MeV) fluences up to 1.8 × 10²⁷ neutrons/m² and thermal (<0.025 eV) fluences up to 3.0 × 10²⁷ neutrons/m². The corresponding maximum displacement level was 260 displacements per atom, and over 7 weight percent silicon was created from transmutation reactions. The major microstructural defects were voids, dislocations, and a precipitate of silicon. Swelling from voids was less than 1 percent. In the “T6” material tested at 323 K (0.35 T_m) and 373 K (0.4 T_m), irradiation raised the 0.2 percent flow stress and the ultimate tensile strength by 45 to 60 percent from the unirradiated values of about 280 and 330 MPa, respectively, ductility was reduced from 15 to about 9 percent. At 423 K (0.45 T_m) there was a similar degree of hardening, but ductility fell to about 5 percent. The alloy in the “0” condition was softer, by 125 to 150 MPa, than the irradiated “T6” alloy, and its elongation remained above 10 percent. In all cases the loss in ductility occurred principally through reduction in uniform strain. Fractures were ductile.