Investigating the structure of iron–chromium alloys using synchrotron based X-ray microanalysis

The Cr in ferritic steels with high Cr content naturally segregates. Depending on the Cr content, the material can be in a state of short-range order (below approximately 10%Cr) or contain clusters of Cr atoms above this concentration. Using synchrotron based X-ray micro-spectroscopy, SEM imaging and fluorescence mapping, Cr-rich clusters in a high purity Fe–16%Cr alloy are identified and investigated. The Cr local structure is resolved by fitting a simple pure Cr model to extended X-ray absorption fine structure (EXAFS) spectra. The fits indicates that the Debye–Waller factor is higher inside the cluster than in the solid solution, but the nearest neighbor distances are closer to that of the pure Cr model inside the cluster than around it.