A high-resolution characterization of the oxide-metal interface in Zircaloy-4 and its relation to the oxidation and hydrogen pickup mechanisms

Oxide growth and hydrogen pickup have been measured for Zircaloy-4 in environments of different pH. The metal-oxide interface has been studied at high-resolution over sufficient lengths to show meaningful trends in the behaviour of the ZrO and oxygen-saturated metal layers (suboxides). It was found that suboxide width decreases rapidly at transition, then increases more slowly. The suboxide width is a constant proportion of the dioxide width prior to transition, but drops then increases after transition. Density functional theory was used to predict suboxide stability under different pressures.