In situ heating TEM analysis of oxide layer formed on Zr-1.5Nb alloy

Zirconium-oxide formed on Zr-1.5Nb alloy was investigated at RT (room temperature) and 360 °C conditions using in situ heating TEM. This characterization of the oxide layer was focused on evaluating the oxide structure and morphology at both RT and 360 °C as a corrosion test temperature in zirconium alloy. It was observed that the monoclinic phase having a columnar morphology formed at the metal/oxide interface was stabilized at both temperatures, whereas some monoclinic phases having equiaxed grains formed at the middle part of the oxide layer were transformed to the tetragonal phase by the increase of the observation temperature from RT to 360 °C. An amorphous precipitate phase incorporated in the oxide layer, which was identified at RT, was crystallized by the temperature change to 360 °C. These variations of oxide property with the observation temperature are related to the difference of thermal expansion between Zr-matrix and ZrO2 phases.