Fractional densities and character of dislocations in different slip modes from powder diffraction patterns

Abstract

Irradiation induced dislocation loops and lattice dislocations produced by plastic deformation have very different dipole characters, dislocation contrasts and range of strain fields. To determine partial dislocation densities of the different dislocation types from X-ray or neutron diffraction patterns, all differences in dislocation properties should be considered. We have extended the convolutional multiple whole profile line profile analysis method to convolve different strain profiles with different effective outer cut-off radii, corresponding to different dislocation type, into a single size profile. The extended procedure is applied to determine the 〈a〉 loop and lattice dislocation densities in a neutron irradiated and tensile deformed Zr-2.5 %Nb alloy and in a proton or neutron irradiated Zircaloy-2 alloy. We show that when the dislocation densities are very different the effective outer cut-off radius of dislocations is a better descriptor of dislocation character than the dislocation arrangement parameter, which was used previously in line profile analysis. Our results show that the combination of line profile analysis and electron microscopy methods provides a detailed and comprehensive description of defect structures in deformed and irradiated materials.