Dislocation electron tomography: A technique to characterize the dislocation microstructure evolution in zirconium alloys under irradiation

Abstract

Diffraction-contrast electron tomography was used to analyse the 3D geometry of the dislocation microstructure in a zirconium alloy before and after ion irradiation. The material had been strained at room temperature prior to irradiation. After straining, the material exhibited mainly screw dislocations with <a> Burgers vectors. From the analysis of the habit plane of <a> dislocations with non-screw segments, it was deduced that they have glided mainly in the prismatic planes and to a lesser extent in the first order pyramidal planes. After irradiation, dislocation loops with <a> Burgers vectors were observed. It was shown that the loops are not pure edge and have their habit plane located around the planes {101¯0}, tilted up to 20° towards the planes (0001) and {112¯0}. Furthermore, it was proven that the initial screw dislocations have climbed under irradiation. Several dislocations were also found to have interacted with loops during climb. The climb of <a> dislocations under irradiation is an important mechanism that can explain part of the in-reactor deformation of zirconium alloys when subjected to simultaneous mechanical loading and irradiation. Interactions between dislocations and loops occurring during dislocation climb may also play a significant role on the in-reactor deformation of zirconium alloys.