The role of alloying elements in the initiation of nanoscale porosity in oxide films formed on zirconium alloys

Zr-Nb-Y alloys were used to investigate the initiation mechanism of nanoscale pores in the oxide films formed on zirconium alloys. Based on the experimental results, we propose that these nanoscale pores are generated by the enrichment of Y at columnar oxide grain boundaries and subsequent unequal diffusion of Y and Zr cations in oxide crystals, which is validated in other two zirconium alloys of M5® and N18. As the generation of porosity is attributed to the characteristics of alloying elements, this work provides a new insight into the effect of alloying elements on the corrosion behaviour of zirconium alloys.