J. Phys. IV France 09 (1999) Pr9-311-Pr9-320
Coupling between diffusion and mechanics during the oxidation of zircaloyM. Parise1, 2, R. Foerch3 and G. Cailletaud1
1 École des Mines de Paris, Centre des Matériaux, UMR 7633 du CNRS, BP. 87, 91003 Evry, France
2 EDF/DER/EMA, Les Renardières, 77818 Moret-sur-Loing cedex, France
3 Northwest Numerics & Modeling Inc., 1219 Westlake Ave., N. Seattle, WA 98109, U.S.A.
During the oxidation of zircaloy fuel cladding, large stresses develop in the oxide layer, due to the volumetric expansion related to phase change. The present paper deals with intermediate temperatures, typically 300-450°C. (1) The first section of the paper shows that the local geometry of interface must be taken into account to correctly describe the local stress field and explain the crack formation. For that purpose, finite element computations are performed with an undulated metal-oxide interface. (2) In a second section, a physical model is proposed to understand why the interface presents this wavy shape. It is assumed that this can be related to the heterogeneous diffusion process in zirconia. A numerical investigation is made using a 2D finite element model. The diffusion coefficient being much larger at the grain boundary, a self-organization occurs and produces undulations as observed by SEM. (3) As it is usually observed that pressure influences the diffusion coefficient, coupled computations involving both mechanics and oxidation are then shown.
© EDP Sciences 1999