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Abstract: Structural, cohesive, and magnetic properties of two symmetric $\Sigma3111$and $\Sigma5210$ tilt grain boundaries GBs in pure bcc Fe and in diluteFeCr alloys are studied from first principles. Different concentration andposition of Cr solute atoms are considered. We found that Cr atoms placed inthe GB interstice enhance the cohesion by 0.5-1.2 J-m$^2$. Substitutional Cr inthe layers adjacent to the boundary shows anisotropic effect on the GBcohesion: it is neutral when placed in the 111 oriented Fe grains, andenhances cohesion by 0.5 J-m$^2$ when substituted in the boundary layer ofthe 210 grains. The strengthening effect of the Cr solute is dominated by thechemical component of the adhesive binding energy. Our calculations show thatunlike the free iron surfaces, Cr impurities segregate to the boundaries of theFe grains. The magnetic moments on GB atoms are substantially changed and theirvariation correlates with the corresponding relaxation pattern of the GBplanes. The moments on Cr additions are 2-4 times enhanced in comparison withthat in a Cr crystal and are antiparallel to the moments on the Fe atoms.



Autor: E. Wachowicz, T. Ossowski, A. Kiejna

Fuente: https://arxiv.org/



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