Combined atom probe tomography and density functional theory investigation of the Al off-stoichiometry of κ-carbides in an austenitic Fe-Mn-Al-C low density steel

Atom probe tomography measurements have been performed to determine the composition of κ-carbides, which is important for the hardening effect of these precipitates in Fe-Mn-Al-C quaternary alloys. We observe a systematic off-stoichiometric Al content, which is analysed in combination with density functional theory calculations. We reveal that an intriguing combination of elastic strain minimization by anti-site defects and C vacancies in their vicinity can explain this phenomenon.291