Irradiation hardening and annealing in copper at high neutron fluences

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Abstract
Irradiation hardening has been investigated in copper crystals irradiated at ∼325 K with 4 × 1020 and 8 × 1020 n cm−2. In the as-irradiated crystals, cleared channels were produced due to the sweeping up of the irradiation damage by the glide dislocations. The slip band width, spacing and height all increased with increasing testing temperature. Identical post-irradiation annealing treatments produced a larger fractional recovery of the critical resolved shear stress at 4 K than at 295 K. This indicates that the damage removed in the early stages of annealing acts as a more effective obstacle to dislocation glide at 4 K than at 295 K. For certain combinations of annealing treatment and low temperature testing, the initial stage of deformation was characterized by the bowing of the glide dislocations around the defects rather than sweeping them up. In polycrystalline copper, migrating grain and twin boundaries were quite effective in sweeping out the irradiation-produced defects.