Electron microscopy of oxide films on Zircaloy-2

Initial oxide films formed on Zircaloy-2 in steam at 750 deg C for periods of 10 and 20 s have been studied using transmission electron microscopy. The initial oxide film is seen to be amorphous but rapidly starts crystallizing during examination. The crystallization product is a mixture of tetragonal and monoclinic oxides. The film obtained at 750 deg C after 20 s of oxidation is fully crystalline and is in the cubic phase of oxide. Delineation of substrate grains in this case is clearly seen. The formation of metastable phases of the oxide has been explained. The orientation relationship between the metal and the oxide has been determined.