Tuning mechanical properties of ultrafine-grained tungsten by manipulating grain boundary chemistry

Michael Wurmshuber, Severin Jakob, Simon Doppermann, Stefan Wurster, Rishi Bodlos, Lorenz Romaner, Verena Maier-Kiener, Daniel Kiener

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung

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Abstract

Tungsten is, due to a combination of high strength and good physical properties, frequently considered for high-performance applications in the harshest environments. Oftentimes its inherent brittleness and low ductility stand in the way of a successful deployment in these fields. Since tungsten has been proposed as divertor material for nuclear fusion reactors, an improvement of ductility and fracture toughness is essential. An obvious first step to increase these properties is to reduce the grain size to the ultrafine-grained regime. As this still leaves the material with a relatively low-energy intercrystalline fracture mode, this work takes a step further. With the help of doping elements, which are identified from ab-initio simulations, an attempt to increase grain boundary cohesion of ultra-fine grained tungsten to improve ductility is made. After fabrication of the doped samples from powders using severe plastic deformation, thorough microstructural investigations and extensive mechanical characterization, utilizing various small-scale testing techniques, are combined to assess the properties of the materials. We report that the addition of boron and hafnium can significantly increase the bending strength and bending ductility of ultra-fine grained tungsten. An additional heat treatment of the boron doped sample amplifies this effect even further, drastically increasing the strength and overall mechanical properties due to a combination of hardening-by-annealing and increased grain boundary segregation. Thus, an effective way to adaptively improve the mechanical properties of tungsten by manipulating grain boundary chemistry is reported, validating grain boundary segregation engineering as a powerful tool for enhancing damage tolerance in brittle materials.
OriginalspracheEnglisch
Aufsatznummer117939
Seitenumfang13
FachzeitschriftActa materialia
Jahrgang232.2022
Ausgabenummer15 June
DOIs
PublikationsstatusElektronische Veröffentlichung vor Drucklegung. - 19 Apr. 2022

Bibliographische Notiz

Funding Information:
The authors acknowledge funding by the European Research Council under Grant number 771146 (MW, SD, DK). The authors thank Dr. Wolfram Knabl, Dr. Judith Köstenbauer and Plansee SE for providing tungsten material powder and support with sample annealing.

Publisher Copyright:
© 2022

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