Effect of heat treatment on the local atomic structure of cementite Fe3C in steel

The extended energy-loss fine structure (EELFS) spectroscopy was used to analyze the response of the nearest neighborhood of carbon atoms in the lattice of cementite Fe3C to heat treatment. For the study of the local atomic structure of the U15 steel after different heat treatments, the electron energy loss spectra were obtained beyond the carbon K edge. The experimental EELFS spectra were treated by the standard technique employed for processing EXAFS (extended X-ray absorption fine structure) spectra, i.e., using the Fourier transformation for determining the parameters of the nearest atomic neighborhood. A qualitative conclusion was made that heat treatment affects the number of iron atoms in the nearest neighborhood of carbon atoms in cementite. This conclusion is based on the changes in the ratio between the intensities of two first maxima of the radial atom distribution functions and is consistent with Mossbauer data.