Ab initio explanation of disorder and off-stoichiometry in Fe-Mn-Al-C kappa carbides

0478839 - ÚFM 2018 RIV US eng J - Journal Article
Dey, P. - Nazarov, R. - Dutta, B. - Yao, M. - Herbig, M. - Friák, Martin - Hickel, T. - Raabe, D. - Neugebauer, J.
Ab initio explanation of disorder and off-stoichiometry in Fe-Mn-Al-C kappa carbides.
Physical Review B. Roč. 95, č. 10 (2017), č. článku 104108. ISSN 2469-9950. E-ISSN 2469-9969
R&D Projects: GA ČR(CZ) GA16-24711S; GA MŠMT(CZ) LQ1601
Institutional support: RVO:68081723
Keywords : steels * nano-composites * elasticity * thermodynamics * quantum-mechanical calculations
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 3.813, year: 2017

Carbides play a central role for the strength and ductility in many materials. Simulating the impact of these precipitates on the mechanical performance requires knowledge about their atomic configuration. In particular, the C content is often observed to substantially deviate from the ideal stoichiometric composition. In this work, we focus on Fe-Mn-Al-C steels, for which we determined the composition of the nanosized kappa carbides (Fe,Mn)3AlC by atom probe tomography in comparison to larger precipitates located in grain boundaries. Combining density functional theory with thermodynamic concepts, we first determine the critical temperatures for the presence of chemical and magnetic disorder in these carbides. Second, the experimentally observed reduction of the C content is explained as a compromise between the gain in chemical energy during partitioning and the elastic strains emerging in coherent microstructures. © 2017 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Permanent Link: http://hdl.handle.net/11104/0275553