Effect of neutron irradiation on deformation mechanisms operating during tensile testing of Zr–2.5Nb

In situ neutron diffraction has been carried out on fast neutron irradiated Zr–2.5Nb pressure tube and non-irradiated Zr–2.5Nb pressure tube samples, with tensile deformation applied along two texture directions. Through the evolution of intergranular strains with applied stress, as measured via the lattice strains of individual grain families, the deformation mechanism of the pressure tube material with and without fast neutron irradiation has been studied. Prismatic , basal and pyramidal has been found to operate in both irradiated and non-irradiated Zr–2.5Nb alloy at different stress levels. Furthermore, by line profile analysis, it is shown that the density of type dislocations in the irradiated sample changed very little during deformation, whereas the density of pyramidal dislocations increased continuously with plastic strain once plastic deformation started. Therefore, it is found that the neutron irradiation induced defects selectively harden prismatic and basal slip, and have very small impact on the operation of pyramidal slip system.

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