Internal stresses and textures of nanostructured alumina scales growing on polycrystalline Fe3Al alloy

Abstract

The evolution of internal stresses in oxide scales growing on polycrystalline Fe3Al alloy in atmospheric air at 700 °C was determined using in situ energy-dispersive synchrotron X-ray diffraction. Ex situ texture analyses were performed after 5 h of oxidation at 700 °C. Under these conditions, the oxide-scale thickness, as determined by X-ray photoelectron spectroscopy, lies between 80 and 100 nm. The main phase present in the oxide scales is α-Al2O3, with minor quantities of metastable θ-Al2O3 detected in the first minutes of oxidation, as well as α-Fe2O3. α-Al2O3 grows with a weak (0001) fiber texture in the normal direction. During the initial stages of oxidation the scale develops, increasing levels of compressive stresses which later evolve to a steady state condition situated around −300 MPa.