Anomalies in carbon concentration determinations from nanostructured bainite

Abstract

There are large discrepancies in the measured concentrations of carbon in the ferrite and austenite within nanostructured bainite and carbide-free bainitic steels in general. The concentrations are usually measured on the basis of lattice parameters determined using X-ray diffraction, lattice imaging in transmission microscopy, or using the atom probe technique, i.e. time-of-flight mass spectroscopy. We examine here a number of difficulties with these methods and assess the role of defects, crystal symmetry and the heterogeneous distribution of carbon in interpreting the experimental data. Issues where experimental and theoretical work is needed are identified.