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The brittle-to-ductile transition in cold-rolled tungsten sheets: the rate-limiting mechanism of plasticity controlling the BDT in ultrafine-grained tungsten

Bonnekoh, Carsten; Reiser, Jens; Hartmaier, Alexander; Bonk, Simon; Hoffmann, Andreas; Rieth, Michael

Abstract:
Conventionally produced tungsten (W) sheets are brittle at room temperature. In contrast to that, severe deformation by cold rolling transforms W into a material exhibiting room-temperature ductility with a brittle-to-ductile transition (BDT) temperature far below room temperature. For such ultrafine-grained (UFG) and dislocation-rich materials, the mechanism controlling the BDT is still the subject of ongoing debates. In order to identify the mechanism controlling the BDT in room-temperature ductile W sheets with UFG microstructure, we conducted campaigns of fracture toughness tests accompanied by a thermodynamic analysis deducing Arrhenius BDT activation energies. Here, we show that plastic deformation induced by rolling reduces the BDT temperature and also the BDT activation energy. A comparison of BDT activation energies with the trend of Gibbs energy of kink-pair formation revealed a strong correlation between both quantities. This demonstrates that out of the three basic processes, nucleation, glide, and annihilation, crack tip plasticity in UFG W is still controlled by the glide of dislocations. The glide is dictated by the mobility of the screw segments and therefore by the underlying process of kink-pair formation. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000120012
Veröffentlicht am 05.06.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Angewandte Materialien - Angewandte Werkstoffphysik (IAM-AWP)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 0022-2461, 1573-4803
KITopen-ID: 1000120012
HGF-Programm 31.03.09 (POF III, LK 01)
Strukturmaterial f. Blanket und Divertor
Erschienen in Journal of materials science
Vorab online veröffentlicht am 19.05.2020
Nachgewiesen in Scopus
Web of Science
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