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Density functional theory study of ω-phase in steel with varied alloying elements
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  • S. Assa Aravindh,
  • Sakari Pallaspuro,
  • Wei Cao,
  • Mahesh Somani,
  • Matti Alatalo,
  • Marko Huttula,
  • Jukka Komi
S. Assa Aravindh
University of Oulu
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Sakari Pallaspuro
University of Oulu
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Wei Cao
University of Oulu
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Mahesh Somani
University of Oulu
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Matti Alatalo
University of Oulu
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Marko Huttula
University of Oulu
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Jukka Komi
University of Oulu
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Abstract

The presence of long abandoned, hexagonal omega (ω) phase in steel samples is recently gaining momentum on account of accurate transmission electron microscopy (TEM) measurements. The formation and stabilization of this metastable phase down to room temperature is attributed to the combined effect of factors such as accelerated cooling, special atomic constraints at twin boundaries, and the enrichment of solute elements such as Al, Mn, Si, C, and Cr in the nanometer sized regimes. Here, we present a density functional theory (DFT) study of the effect of the above alloying elements in ω-Fe and confirm the predictions using high resolution TEM observations of the structure of an experimental steel at high magnifications. It is found that the FM and ++- spin states are the most stable for a primitive cell of ω-Fe. The density of states calculations show that the d band occupancy of ω-Fe is changing in presence of the alloying elements, and this in turn will affect the cohesive energy. Further, the dynamical stability analysis from phonon band structure reveals that only ω-Fe with substitutional C exhibits thermodynamic stability. This is in line with experimental indications that the stabilization of ω-phase in ferritic/martensitic steels occurs due to the presence of special symmetry constraints at grain boundaries

Peer review status:ACCEPTED

05 Dec 2019Submitted to International Journal of Quantum Chemistry
06 Dec 2019Submission Checks Completed
06 Dec 2019Assigned to Editor
09 Dec 2019Reviewer(s) Assigned
20 Dec 2019Review(s) Completed, Editorial Evaluation Pending
20 Dec 2019Editorial Decision: Revise Minor
11 Jan 20201st Revision Received
13 Jan 2020Assigned to Editor
13 Jan 2020Submission Checks Completed
27 Jan 2020Reviewer(s) Assigned
11 Feb 2020Review(s) Completed, Editorial Evaluation Pending
11 Feb 2020Editorial Decision: Revise Minor
14 Feb 20202nd Revision Received
15 Feb 2020Submission Checks Completed
15 Feb 2020Assigned to Editor
17 Feb 2020Reviewer(s) Assigned
04 Mar 2020Review(s) Completed, Editorial Evaluation Pending
11 Mar 2020Editorial Decision: Accept