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Linear complexions: Confined chemical and structural states at dislocations

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Science  04 Sep 2015:
Vol. 349, Issue 6252, pp. 1080-1083
DOI: 10.1126/science.aab2633

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Welcoming steel's new complexion

Metals have a number of famous properties, including good strength and ductility. Controlling these properties frequently requires modifying the number and type of structural defects in a metal alloy. Kuzmina et al. produced a new type of defect, called a linear complexion, in magnesium-rich steel (see the Perspective by Kaplan). These complexions are chemically and structurally distinct regions located inside a linear defect and are isolated from the bulk by a layer of dislocations. The discovery suggests a new path for targeting defects and improving alloy development.

Science, this issue p. 1080; see also p. 1059

Abstract

For 5000 years, metals have been mankind’s most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe–9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states.

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