Regensburg 2019 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 24: Topical session (Symposium MM): Correlative and in-situ Microscopy in Materials Research

MM 24.9: Vortrag

Mittwoch, 3. April 2019, 13:00–13:15, H45

Fracture toughness of predeformed chromium studied with microcantilever bending — •Stefan Gabel, Benoit Merle, Erik Bitzek, and Mathias Göken — Institute I: General Materials Properties, FAU Erlangen-Nürnberg, Germany

Cr, Mo and W are the most common bcc metals, which are characterized by a high melting point and high strength. However their fracture toughness at room temperature is low. This is due to their rather high ductile by brittle transition temperature. At room temperature the fracture toughness is limited by dislocation mobility or by the inability to activate nucleation sources. While this behavior is well researched for W, there are only few studies for Cr. FIB milled cantilevers were used to characterize the facture toughness of Cr on the microscale and to study the influence of the loading rate and the initial dislocation density of the sample. In order to achieve high dislocation densities by pre-deformation, Vickers indentations were made on the sample surface prior to testing. The resulting plastic strain field in the material was analyzed by FEM. Selecting different distances to the center of the Vickers indent allows varying the amount of pre-deformation of the cantilevers. The measurements showed that an increase of the loading rate embrittles Cr, whereas an increase of the dislocation density leads to a toughening of the sample. Furthermore the dependence of the transition in the fracture behavior on the availability dislocations and activity of dislocations sources was investigated via TEM-lamella lift-outs and Transmission Kikuchi Diffraction mapping.