Strong rotated cube textures in thin cold-rolled potassium-doped tungsten sheets during annealing up to 1300 °C

D Tarras Madsen,W Pantleon,A Hoffmann,U M Ciucani

doi:10.1088/1757-899x/1121/1/012018

D Tarras Madsen, W Pantleon + Show 2 more

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https://doi.org/10.1088/1757-899x/1121/1/012018

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Abstract

Due to the high operation temperatures, microstructural changes will occur in tungsten when used as plasma-facing material in future fusion reactors. In drawn tungsten wires, potassium doping has proven to prevent such undesired changes effectively. This strategy has been adapted to thin cold-rolled tungsten sheets containing 80 ppm potassium. Their texture evolution during annealing is investigated using electron backscatter diffraction. In the as-rolled condition, a strong cube texture is present with a volume fraction of 67.0 % deviating maximal 15° from the rotated cube orientation. This texture intensifies strongly during isochronal annealing for 2 h at temperatures between 1000 °C and 1300 °C; the higher the temperature, the higher the rotated cube fraction. The volume fraction of 94.8 % obtained after 2 h at 1300 °C does not change significantly during further annealing. These are remarkably strong textures for a body-centered cubic metal compared e.g. to commonly reported high volume fractions of 30 % for Goss orientations in silicon steels. Reliable quantification of such strong texture components requires analysis of orientations individually.

Highlights

Tungsten is considered for plasma-facing components in future fusion reactors as armor material for the first wall and the divertor
The texture evolution during annealing of cold-rolled tungsten sheets with a comparably high potassium content of 80 ppm is investigated in detail
The orientation distribution function (ODF) section reveals a strong preference of orientations with Euler angles (φ1,Φ,φ2) = (0°,0°,45°)

Summary

Introduction

Tungsten is considered for plasma-facing components in future fusion reactors as armor material for the first wall and the divertor. Pure annealed tungsten has a high brittle-to-ductile transition temperature and behaves brittle at room temperature [1] restricting its use as plasma-facing material. During operation as plasma-facing component at high temperatures, the deformation structure induced by plastic deformation becomes unstable. Several concepts have been pursued to increase the thermal stability of the microstructure or at least to control the microstructural changes by restricting the motion of grain boundaries. Such an impedance of grain boundary motion can be achieved by alloying tungsten with dispersed oxides or carbides pinning the grain boundaries The texture evolution during annealing of cold-rolled tungsten sheets with a comparably high potassium content of 80 ppm is investigated in detail

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