Characterization Of Selective Oxidation Of Manganese In Surface Layers Of Fe-Mn Alloys By Different Analytical Methods

Since selective oxidation of alloying elements on the surface of-steel products influences their surface properties, characterization of the surface oxides which can be considered as non-metallic inclusions is of great importance. In this study, X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD) and X-ray absorption spectroscopy (XAS) were used for characterizing the formation process of Mn oxides on the surface of annealed Fe-Mn alloys under a low partial pressure of oxygen. The results obtained by XPS showed that the enrichment and oxidation of Mn occurs on the surface of the Fe-Mn alloys annealed under low oxygen partial pressure, and Mn oxides are formed in the metallic Fe matrix in the surface layers. XAS spectra using grazing-exit X-ray fluorescence measurements showed depth-resolved information on chemical state of Mn. These Mn oxides were identified as MnO (manganosite) by grazing-incident XRD measurements. It was found using in situ XRD measurements at high temperatures that the lattice constant of MnO increased with increasing annealing temperature, which attributed to the non-stoichiometry of MnO. These oxidation characteristics of Mn in the Fe-Mn alloys are discussed on the basis of thermochemical properties of Mn.