Dresden 2020 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 44: Topical Session: Interface-dominated phenomena - Solutes at Interfaces II

MM 44.3: Talk

Wednesday, March 18, 2020, 17:45–18:00, IFW A

Ag segregation induced nanofaceting transition of a Cu tilt grain boundary and its impact on plastic deformation mechanisms — •Nicolas J. Peter, Christian H. Liebscher, Christoph Kirchlechner, and Gerhard Dehm — Max-Planck Insitut für Eisenforschung GmbH

We describe the observation of a nanofaceting transition of an asymmetric tilt GB in Cu upon Ag segregation by atomically resolved scanning transmission electron microscopy. The initially flat {110}/{410} boundary was found to dissociate into Ag-lean {230}/{100} asymmetric facet segments and Ag-rich symmetric {210} segments. Thus, a preferential segregation pattern of stable nanosized facets was found. Further, the influence of Ag solute excess concentration on the facet formation was studied by a diffusion couple. It was found that the asymmetric segment remains constant in size, while the symmetric facet segment increases with increasing solute excess. At the diffusion couple's interface a purely symmetric {210} boundary is found. Following the GB, short asymmetric facet segments are introduced and increase their density until a purely asymmetric GB is found close to the non-segregated reference state. Finally, we linked the observed faceting transition to a change in plastic deformation behaviour by tensile straining GB containing bicrystals in situ inside the electron microscope. While pure Cu reference boundaries deform by local emission of partial dislocations resulting in the formation of a single deformation twin, the Ag segregated bicrystal shows numerous partial dislocation nucleation sites resulting in an increase of deformation twins.