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MM: Fachverband Metall- und Materialphysik

MM 40: Topical Session: Interface-dominated phenomena - Solutes at Interfaces I

MM 40.2: Vortrag

Mittwoch, 18. März 2020, 16:15–16:30, IFW A

Atomic scale structure and segregation behavior at Σ5 tilt grain boundaries in bcc iron — •Ali Ahmadian, Xuyang Zhou, Christian H. Liebscher, and Gerhard Dehm — Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

Grain boundaries (GBs) are two-dimensional defects, which determine the mechanical as well as physical properties of polycrystalline materials. Segregation of impurities, such as phosphorous, to GBs can reduce their cohesive strength and with this lead to embrittlement of a material. By introducing other impurities such as carbon, the segregation tendency of phosphorous can be suppressed. It is under debate whether boron has the same effect as carbon and how a co-segregation of both elements influences GB properties [1]. In this work, we investigated ferritic Fe-2wt%Al bicrystals grown by a modified Bridgeman technique. The global structure of the GB is characterized by electron backscatter diffraction, revealing a symmetric Σ5 [001] (310) tilt GB. Aberration-corrected scanning transmission electron microscopy experiments showed kite-type structural units as predicted by atomistic simulations by Scheiber et al. [2]. However, the atomic structure of the GB also contains other defects such as facets or steps, leading to different local reconstructions. In combination with atom probe tomography experiments, a clear segregation of both carbon and boron is observed, while aluminium is depleted at the boundary. The latter one is in contradiction to DFT calculations, where a clear segregation of aluminium was predicted. [1] C. M. Liu et al., Metall Trans A 23 (1992) [2] D. Scheiber et al., MODEL SIMUL MATER SC 24 (2016)