Oxide/α and α/β phase interface advance kinetics in steam oxidised zircaloy-2

Weight gain kinetics and phase interface advance measurements on specimens of zircaloy-2 oxidised at temperatures between 10300 and 14000C are presented. The observed positions of the oxide/alpha and alpha/beta interfaces are compared with the predictions of a diffusion model of the process. Using previously recommended oxygen diffusion coefficients, agreement between theory and experiment is obtained at temperatures above 11000C when oxygen saturation of the beta phase promotes isothermal growth of alpha phase incursions during oxidation. At temperatures below 11000C, incursion growth occurs only on quenching. Agreement between prediction and observation is then obtained by excluding the alpha phase component which precipitates onto the isothermally formed alpha/beta boundary during quenching from the oxidation temperature. (orig.)