Comparison of K-doped and pure cold-rolled tungsten sheets: Tensile properties and brittle-to-ductile transition temperatures

JOURNAL OF NUCLEAR MATERIALS

卷:544

Article

Lied, Philipp¹  Pantleon, Wolfgang²  Bonnekoh, Carsten¹  Bonk, Simon¹  Hoffmann, Andreas³  Reiser, Jens^1,4  Rieth, Michael¹ 

[1] Karlsruhe Inst Technol, Inst Appl Mat Appl Mat Phys, D-76344 Eggenstein Leopoldshafen, Germany

[2] Tech Univ Denmark, Dept Mech Engn, Sect Mat & Surface Engn, DK-2800 Lyngby, Denmark

[3] PLANSEE SE, A-6600 Reutte, Austria

[4] Precitec GmbH & Co KG, D-76571 Gaggenau, Germany

关键词: Cold-rolling;    Potassium-doping;    Recrystallization inhibition;    Fracture toughness;    Tensile strength;    Hall-Petch relation;   

DOI  :  10.1016/j.jnucmat.2020.152664

来源: Elsevier

【 摘 要 】

For high-temperature environments, as in future fusion reactors, the use of tungsten materials has been sincerely discussed in the last decade. Although severe cold-rolling of tungsten leads to significant improvements in mechanical properties, the fine-grained microstructure of such tungsten material has to be stabilized. For that, the use of potassium-doping (K-doping) in tungsten sheets is investigated in our ongoing study. In this work, we compare mechanical properties of warm- and cold-rolled sheets of pure tungsten and K-doped tungsten (for five different degree of deformation respectively) by means of fracture toughness tests and tensile tests. Fracture toughness and brittle-to-ductile transition temperatures (T-BDT) are assessed, showing a slightly lower transition temperature for the cold-rolled K-doped sheets (lower than -100 degrees C for the 50 mu m thick foil). The better performance of the K-doped sheet is related to its finer grain size. The thickest K-doped sheet shows a much higher T-BDT than its pure tungsten counterpart. This is presumably caused by the presence of several tens of micrometre thick bands, containing only low angle boundaries, in the microstructure of the K-doped sheet. Tensile tests reveal an outstanding yield strength of 2860 MPa and an ultimate tensile strength of 2970 MPa for the thinnest K-doped sheet with similar, but slightly lower values for the pure tungsten counterpart. Both thinnest sheets show a drastic increase in ultimate tensile strength in correlation to their mean grain size, much higher than expected by a Hall-Petch relation. This deviation has been observed for the microhardness as well and is assumed to be caused by an extraordinary increase in the density of dislocations. Our results indicate that no disadvantages in tensile strength and brittle-to-ductile transition are to be expected compared to pure tungsten, when K-doped tungsten is used to inhibit recrystallization in high-temperature environments. (C) 2020 The Authors. Published by Elsevier B.V.

【 授权许可】

Free