Auger electron spectroscopy and X-ray photoelectron spectroscopy characterization of the oxidation of austenitic Fe-26Mn-7Al-0.9C alloy in atmosphere

Austenitic Fe-26Mn-7Al-0.9C was annealed for 1 h at atmospheric pressure at 200, 400, 600 and 800 C. Low-energy Auger transitions and detail X-ray photoelectron spectra were used to characterize the oxide layers formed on the alloy during annealing at the different temperatures. The oxide layer formed at 200 C contains Al2O3, FeO and MnO. The oxide layers formed at 400 and 600 C consist of a mixture of MnO and Fe2O3. A topmost MnO2 layer was also present at 600 C. Al2O3, FeO and MnO were present at the oxide/alloy interfaces of all the samples. The S impurity in the alloy has no detectable effect on the oxidation process. The grain size of the oxide crystals formed during the annealing process increased from 0.5±0.1 μm at 400 C to 0.9±0.1 μm at 800 C. The grain sizes were determined from atomic force microscope images of the annealed sample surfaces. (orig.)