Detection of segregation within oxide scales by EELS

The segregation of reactive elements to the oxide grain boundaries is thought to play a vital role in the improvement of oxidation behaviour of alloys. However, direct evidence as to the presence of segregated elements at the oxide grain boundaries or at the scale-alloy interface is not widespread due to experimental difficulties. In the present study, electron-energy-loss spectroscopy (EELS) coupled with transmission-electron microscopy (TEM) was used to detect this type of segregation. An ODS MA956 type alloy with 0.7% Y₂O₃ oxidized in air for 100 hours at 1200°C was examined by EELS in TEM. A shift in position and a change in the shape of the plasmon loss obtained from the oxide grain boundaries were observed indicating the presence of segregated elements at these regions.