Effects of neutron irradiation on microstructure and mechanical properties of pure iron

Tensile specimens of pure iron were irradiated with fission neutrons (i) at 320 K to displacement dose levels of 7.5 × 10 ^-3, 7.5 × 10 ^-2 and 3.75 × 10 ^-1 dpa (NRT) and (ii) at 523 K to dose levels of 7.5 × 10 ^-2 and 2.25 × 10 ^-1 dpa (NRT). Both unirradiated and irradiated specimens were tensile tested at the irradiation temperatures. Microstructures of the as-irradiated and irradiated and tensile tested specimens were investigated by transmission electron microscopy. Fracture surfaces of tensile tested specimens in unirradiated and irradiated conditions were examined in a scanning electron microscope. Results of these investigations are reported and discussed particularly in terms of the role of interstitial clusters (produced directly in the cascades) and their transport via one-dimensional glide. It is suggested that the formation and interaction of `cleared' channels may play a significant role in determining the deformation and fracture behaviour of the irradiated pure iron.