Dislocation core reconstruction induced by carbon segregation in bcc iron

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2015-06, Vol.91 (22), Article 220102
• Main Authors: Ventelon, Lisa, Lüthi, B., Clouet, E., Proville, L., Legrand, B., Rodney, D., Willaime, F.
• Format: Article
• Language: English
• Subjects: Carbon; Chemical Sciences; Condensed matter; Density functional theory; Dislocations; Engineering Sciences; Hardness; Physics; Precipitation hardening; Reconstruction; Saturation
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.91.220102

The relative stability of dislocation core configurations in body-centered-cubic metals is profoundly modified by the presence of solutes. Considering the Fe(C) system, we demonstrate by using density functional theory that carbon atoms destabilize the usual easy core to the benefit of the hard core configuration of the screw dislocation, which is unstable in pure metals. The carbon atom is at the center of a regular prism in a cementite like local environment. The same dislocation core reconstruction is also found with other solutes (B, N, O) and in W(C). This unexpected low-energy configuration induces a strong solute-dislocation attraction, leading to dislocation core saturation by solute atoms, even for very low bulk solute concentrations. This core reconstruction will constitute an essential factor to account for in solute-segregation related phenomena, such as strain aging.