TY - JOUR

T1 - Tuning mechanical properties of ultrafine-grained tungsten by manipulating grain boundary chemistry

AU - Wurmshuber, Michael

AU - Jakob, Severin

AU - Doppermann, Simon

AU - Wurster, Stefan

AU - Bodlos, Rishi

AU - Romaner, Lorenz

AU - Maier-Kiener, Verena

AU - Kiener, Daniel

N1 - Publisher Copyright: © 2022

PY - 2022/4/19

Y1 - 2022/4/19

N2 - 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.

AB - 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.

UR - https://pure.unileoben.ac.at/portal/en/publications/tuning-mechanical-properties-of-ultrafinegrained-tungsten-by-manipulating-grain-boundary-chemistry(6c26cde8-3c12-4228-a8e6-f3a78f21fa21).html

UR - http://www.scopus.com/inward/record.url?scp=85129471007&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2022.117939

DO - 10.1016/j.actamat.2022.117939

M3 - Article

VL - 232.2022

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 15 June

M1 - 117939

ER -