Radiation damage and the effects of postirradiation annealing in 1100 grade aluminum

Abstract

Transmission electron microscopy and immersion density measurements were used to characterize radiation damage and postirradiation annealing effects in annealed 1100 aluminum irradiated at 45 °Cin an aqueous environment to maximum fluences of 3.2 × 10²² n/cm² (> 0.1 MeV) and 3.1 × 10²² n/cm² (thermal). Radiation-induced swelling from voids was first detected at 7 × 10²¹ n/cm² and reached a value of 1.5 per cent at 3.2 × 10²² n/cm² with a void concentration of 1.8 × 10¹⁴/cm³. Transmutation-produced silicon, from thermal neutron reactions with ²⁷Al, formed fine precipitate particles of approximately 5 × 10¹⁵/cm³, uniformly distributed throughout the matrix.

Irradiation-induced swelling began to anneal out in 1 hr between 110 to 170°C, with complete elimination of voids between 300-350 °C. Subsequent annealing at higher temperatures resulted in the growth of transmutation gas bubbles and renewed swelling. No helium loss was detected in 20 hr postirradiation anneals at 560°C. The activation energy for void annealing, determined from isochronal and isothermal density recovery measurements in in the temperature range 170 to 300°C, was found to be in the range 1.8 to 2.0 eV. Void annealing occurred by the preferential elimination of all voids near grain boundaries as well as the smaller voids within grains. Significant void coarsening occurred within the grains before eventual elimination.