Influence of oxygen impurity atoms on defect clusters and radiation hardening in neutron-irradiated vanadium

Single crystal TEM samples and polycrystalline tensile samples of vanadium containing 60-640 wt ppM oxygen were irradiated at about 1000C to about 1.3 x 1019 neutrons/cm2 (E greater than 1 MeV) and post-irradiation annealed up to 8000C. The defect cluster density increased and the average size decreased with increasing oxygen concentration. Higher oxygen concentrations caused the radiation hardening and radiation-anneal hardening to increase. The observations are consistent with the nucleation of defect clusters by small oxygen or oxygen-point defect complexes and the trapping of oxygen at defect clusters upon post-irradiation annealing