Oxidation upon segregation: Evaluation of chemical state of segregated species in polycrystalline Fe-Si-Al alloys by AES

Oxidation state of individual alloying elements (Si, Al) and impurity element (Cu) upon segregation onto the surface of the sample Fe-Si-Al alloys was investigated in an in situ study of segregation behavior in ultra-high vacuum. Chemical state of surface Si, Al and O as well as Cu was evaluated, by measuring the kinetic energy shifts that affect Si KLL, Al KLL, O KLL but also Cu LMM transitions, depending on chemical state of the element. It was found that Al oxidizes with temperature in all samples while Si behaves differently with maximum oxidation occurring around 300 °C, and oxidation not occurring at all in some samples. Segregated Cu stays predominantly in its elemental state which is consistent with relevant literature reports.