Evolution of cleared channels in neutron-irradiated pure copper as a function of tensile strain

Tensile specimens of pure copper were neutron irradiated at ∼323 K to a displacement dose of 0.3 dpa (displacement per atom). Five irradiated specimens were tensile tested at 300 K, but four of the specimens were stopped at specific strains – just before the yield point at ∼90% of the macroscopic yield, at 1.5% and 5% elongation, and near the ultimate tensile strength at 14.5% elongation, with the 5th specimen tested to failure (eT=22%). SEM and TEM characterization of the deformed specimens revealed that the plastic strain was confined primarily to the `clearedʹ channels only, and that channels were present in a low number even before the macroscopic yield. New primary channels and secondary channels continued to form with increasing strain, suggesting the increase in stress was related directly to the initiation of new channels as earlier sources were exhausted.