DYNAMICAL DIFFUSION-MODEL TO SIMULATE THE OXIDE CRYSTALLIZATION AND GRAIN-GROWTH DURING OXIDATION OF ZIRCONIUM AT 573-K AND 623-K

A dynamical diffusion model is presented that is able to describe the parabolic and cubic behavior of the pre-transition oxidation kinetics of polycrystalline zirconium in dry oxygen during isothermal oxidation treatments at 573 acid 623 K. The model considers that the processes of crystallization and grain growth during oxidation modify the oxygen diffusion coefficient, by decreasing the number of short circuit path s in the oxide. The change of the oxygen diffusion coefficient is rela ted with the ''time at temperature'' of each oxide layer formed at the oxide/metal interphase boundary.