The effects of neutron irradiation on the physicomechanical properties of refractory metals

Abstract

Studying the interaction of radiation defects with defects in the crystal lattice in the initial state makes it possible to distinguish the contribution of each type of defect to changes in the physicomechanical properties of materials exposed to irradiation. When comparing the changes in the properties of the metals with the body-centered cubic (BCC) lattice (Mo, W, V, Nb) and hexagonal close-packed (HCP) lattice (Re), we see common features and differences in their behavior under irradiation: − both HCP and BCC crystals show an orientation dependence of their properties; at the same time, the metals with the BCC lattice are characterized by an increase in the size of the sample in all crystallographic directions, whereas, for the HCP crystals, the sample is narrowed along the <0001> direction, perpendicular to the plane with the closest packing of atoms, and expanded along other directions; − for the BCC samples, the elastic moduli decrease; for the HCP samples, the shear modulus increases significantly as a result of irradiation; − electrical resistance for the metals of Group 6 (Mo, W) and rhenium as a result of irradiation increases; for the metals of Group 5 (V, Nb), it decreases: this decrease in electrical resistance is associated with the release of interstitial impurity atoms to radiation defects; − for the BCC crystals, relaxation processes occur both in the unirradiated and irradiated samples, whereas, in the HCP crystals, only irradiation and post-irradiation annealing cause the temperature dependence of internal friction (TDIF) and the appearance of a relaxation maximum due to a change in the point symmetry of the defect; and − during isochronous annealings up to 0.7×Тm, behavior features associated with the crystal lattice structure are retained.