Effects of Neutron Irradiation and Annealing on the Elastic Moduli and Electrical Resistivity of Molybdenum and Tungsten Single Crystals

The effects of neutron irradiation and annealing on the elastic moduli and electrical resistivity of Mo and W were studied using single-crystal samples oriented with their axis along [100], [110], and [111]. The samples were irradiated with fast neutrons (E> 0.1 MeV) to a neutron fluence of 1.14 × 1026n/m2in a BR-10 reactor at 460°C. The irradiation-induced changes in resistivity and elastic moduli were found to be orientation-dependent. Irradiated W was found to exhibit elastic anisotropy and relaxation of the shear and Young's moduli. Isochronal annealing below 0.7tmdid not reduce the resistivity of the samples to its initial level, presumably because of the formation of radionuclides, while the shear and Young's moduli were restored to their initial levels.