Atomistic investigations of κ-carbide precipitation in austenitic Fe-Mn-Al-C lightweight steels and the effect of Mo addition

The effect of Mo addition on precipitation behavior of kappa-(Fe,Mn)(3)AlC during aging in austenitic Fe-Mn-Al-C lightweight steels was investigated. First-principles calculations indicate that substitution of Fe or Mn by Mo in kappa-carbide is energetically unfavorable in the respect to formation energy, and it, moreover, increases strain energy contribution to interfacial energy between austenite matrix and kappa-carbide. Atom probe tomography (APT) and transmission electron microscopy (TEM) analysis showed the results consistent with the calculations, i.e., Mo didn't partition into kappa-carbide and delayed kappa-carbide precipitation. Finally, nanoindentation experiments presented that Mo addition changed the aging hardening behavior, corresponding to kappa-carbide precipitation behavior. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.