The effect of Sn–VO defect clustering on Zr alloy corrosion


Density functional theory simulations were used to study Sn defect clusters in the oxide layer of Zr-alloys. Clustering was shown to play a key role in the accommodation of Sn in ${\text{ZrO}\2}$, with the {${\text{Sn}\{\text{Zr}}:\text{V}^{\text{O}}}$}$^×$ bound defect cluster dominant at all oxygen partial pressures below 10−20 atm, above which is preferred. {${\text{Sn}\{\text{Zr}}:\text{V}^{\text{O}}}$}$^×$ is predicted to increase the tetragonal phase fraction in the oxide layer, due to the elevated oxygen vacancy concentration. As corrosion progresses, the transition to ${\text{Sn}{\text{Zr}}^×}$, and resultant destabilisation of the tetragonal phase, is proposed as a possible explanation for the early first transition observed in Sn-containing Zr–Nb alloys.

Corrosion Science
Mark Wenman
Mark Wenman
Senior Lecturer in the Department of Materials