Mechanisms of water chemistry on oxide microstructures in zirconium alloy corrosion: A comparative study via PED-EELS

The corrosion behaviors of a Zr-0.45 Sn-0.38 Nb-0.30 Fe-0.05 Cu-0.015 Si-0.13 O alloy (wt%) was studied after exposure for 300 days in 360 ℃/18.6 MPa pure water, lithiated water and dissolved oxygen (DO) water, respectively. Transmission electron microscopy (TEM) with precession electron diffraction (PED) and electron energy loss spectroscopy (EELS) revealed critical differences in oxide microstructure, texture, and compositional variants across the oxide/metal (O/M) interface. Results demonstrate that Li⁺ induces premature corrosion transition by disrupting columnar grain morphology, increasing grain boundary density, and therefore accelerating O^2- diffusion. In contrast, DO significantly enhanced initial corrosion rate, leading to distorted oxide grains and weakened texture due to rapid oxide growth. Hexagonal ZrO (h-ZrO) suboxide layer at the O/M interface were observed in both lithiated and DO water oxide, with their formation linked to corrosion stage and stress level. Stress-driven texture evolution exhibited periodicity in pure and lithiated water oxides but was absent in DO water due to high grain distortion and suppressed corrosion transition. These findings highlight the critical roles of water chemistry and stress in governing zirconium alloy corrosion mechanisms, offering insights for optimizing nuclear fuel cladding performance in water-cooled reactors.