Abstract
An age-hardening was observed in aluminum-2.2wt% lithium alloy specimens irradiated to a neutron dose of 1.2×1019 cm−2 at 45°C. The specimens were annealed for 4 hr at 350°C prior to the irradiation. Upon heating at temperatures of 155°, 170° and 191°C, the yield stress of the irradiadted specimens increased in two stages following the recovery of radiation-induced hardening, while the yield stress of unirradiated specimens remained unchanged.
The changes in yield stress of the irradiated specimens can be explained as follows. Precipitate particles in the overaged state were destroyed and resolved into the matrix by the irradiation. And the irradiation temperature was too low for the alloy to proceed the precipitation process during the irradiation. Hardening observed in the as-irradiated specimens was due to lattice defects produced by irradiation. Following the recovery of the hardening, precipitation hardening took place in two stages corresponding to the precipitation of spherical and rod-shaped particles.
