Advances in synchrotron x-ray diffraction and transmission electron microscopy techniques for the investigation of microstructure evolution in proton- and neutron-irradiated zirconium alloys

Transmission electron microscopy (TEM) studies provide mechanistic understanding of nanoscale processes, whereas advanced synchrotron XRD (SXRD) enables precise measurements on volumes that are more representative of bulk materials. Therefore, the combined strengths of these techniques can provide new insight into irradiation-induced mechanistic processes. In the present study, their application to Zircaloy-2, proton-irradiated to 2.3, 4.7, and 7.0 dpa at 2 MeV and 350 °C and neutron-irradiated to 9.5 and 13.1 × 1025n m−2are exemplified. The application of correlative spectral imaging and structural TEM investigations to the phase transformation of Zr(Fe,Nb)2precipitates in Low-Sn ZIRLO™, neutron-irradiated to 8.9–9 × 1025n m−2, demonstrates the possibility of a Cr core nucleation site. Anomalous broadening is observed in SXRD profiles, which is believed to be caused by defect clusters and precursors to dislocation loop nucleation. The challenges to quantitative analysis of dislocations by SXRD are highlighted with reference to the segregation of Fe and Ni to basal planes and dislocation cores, observed by spectral imaging in the TEM.