Development of tungsten fibre-reinforced tungsten composites towards their use in DEMO—potassium doped tungsten wire

Riesch, J.; Han, Young‐Soo; Almanstötter, J.; Coenen, J. W.; Höschen, T.; Jasper, B.; Zhao, Pei; Linsmeier, Ch.; Neu, R.

doi:10.1088/0031-8949/t167/1/014006

Cited by 89 publications

(96 citation statements)

References 21 publications

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“…Furthermore, studies regarding the mechanical response and plastic deformation at elevated temperatures showed that the wire can keep its valuable properties [26,27]. Additionally, some investigations dealt with the question of the effect of annealing on tensile properties of pure [28] and potassium doped tungsten wire [29], interconnecting in such a way general microscopic features to different material responses occurring in the experiment.…”

Section: Introductionmentioning

confidence: 99%

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

Nikolić

Riesch

Pippan

2018

Materials Science and Engineering: A

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Advanced tungsten fibre-reinforced composites (Wf/W), showing pseudo ductile behaviour even at room temperature, are a promising option for future fusion reactors as the intrinsic brittleness of tungsten can be mitigated effectively. The drawn tungsten wires used as reinforcements are the key component of the composites, thus their mechanical properties and thermal stability define the allowed operation / fabrication temperature of the composite material itself. In this work, a comprehensive characterization of the pure and potassium doped tungsten wires was performed, focusing on the influence of various heat treatments on different microstructural features (nature of grain boundaries, grain shape and size, texture analyses) and mechanical properties. Annealing in the temperature range from 900-1600°C enables the investigation of the microstructural stability of the two materials and arising annealing phenomenarecovery, recrystallization and grain growth. The results demonstrate that the pure tungsten recrystallizes fully in the temperature range 1300-1500°C accompanied with tremendous coarsening and a complete loss of the initial fibrous, elongated grain structure. In contrast to this, potassium doped wire shows superior high temperature properties, where performed heat treatments cause only milder microstructural changes, consequently suppressing recrystallization and grain growth to temperatures well above the investigated ones. Furthermore, hardness measurements and observed softening complement the discussion of the grain morphology evolution.

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Section: Introductionmentioning

confidence: 99%

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

Nikolić

Riesch

Pippan

2018

Materials Science and Engineering: A

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“…Recently, it is generally recognized that WK is a metal matrix composite because the non-alloyable constituent K, is almost insoluble in W. The K bubble in W is recognized as the strongest pinning phase at high temperatures against the migrations of GBs and dislocations [51]. The excellent performances of the WK filaments at high temperatures make people associate them with the possible applications in nuclear fusion installations [16, 19, 24, 25, 31, 32, 38, [55][56][57][58][59][60][61][62][63]. On the basis of summarizing the previous research work, this paper briefly reviews WK performances including mechanical properties, the resistance to thermal shock, and irradiation tolerance.…”

Section: Pfms and Wkmentioning

confidence: 99%

“…WK wires which displayed good ductility and high strength at high temperatures were used as a reinforced phase to enhance mechanical performances. Literature [57] showed that K-doped W wires could enhance the overall operating temperature and the allowed fabrication temperature of the W-based composite. W-fiber (containing K, W f )-reinforced composites could show pseudo-ductility even at RT.…”

Section: Mechanical Properties Of Wkmentioning

confidence: 99%

Tungsten–potassium: a promising plasma-facing material

2019

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Tungsten-potassium (potassium-doped tungsten or WK), initially known from the electric filament industry, is a promising plasma-facing material (PFM) in future fusion facilities like International Thermonuclear Experimental Reactor (ITER). However, the brittle nature of W and irradiation-induced defects of WK materials may result in a risk of deuterium-tritium reaction failure in fusion reactors. Previous studies revealed that advanced W with ultrafine grains and nanostructures might be able to address these problems. However, K-doped W, a rapidly developed material for PFMs, lacks a systematical summary. In this review, we firstly describe the powder metallurgy and plastic deformation for the preparation of WK. Then, the mechanical properties of WK and thermal shock resistance results are reviewed. Important issues such as irradiation damages from neutron, heavy ion, and plasma (H isotope or He) irradiation are also discussed. Hitherto, WK under irradiations shows comparable or even better performances compared with other counterparts such as ITER grade pure tungsten. This review could be benefitial to the future efforts of improving the ductility and irradiation tolerance of WK materials.

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“…This is the case for tungsten fibers in an 'asfabricated condition' [11]. Thermal treatment during the production of the composite or through operation conditions of the fusion reactor and additional embrittlement due to neutron irradiation can reduce the ductility of the tungsten fibers [12].…”

Section: Tungsten Fiber-reinforced Tungsten (W F /W)mentioning

confidence: 99%

Insight into single-fiber push-out test of tungsten fiber-reinforced tungsten

Schönen

Jasper

Coenen

et al. 2018

Composite Interfaces

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To overcome the intrinsic brittleness of tungsten (W), a tungsten fiber-reinforced tungsten-composite material (W f /W) is a possible solution. The introduction of energy dissipation mechanisms like fiber bridging or fiber pull-out by means of an engineered interface between fiber and matrix mitigate the brittleness of tungsten and lead to a pseudo-ductile material behaviour. The push-out test of single-fiber samples is an experimental method to investigate the properties of the interface between fiber and matrix of composite materials. It is widely used for the investigation of ceramic composites. This method was also used to investigate the debonding and frictional properties of the Er2O3 interface region between fiber and matrix of W f /W single-fiber samples made by CVD-and HIP-processes. In this article finite element calculations are used to get a better understanding of the processes acting in the interface during a push-out test of W f /W. A detailed overview of the debonding progress and of the corresponding stress states of the interface during the different stages of the test is presented. In addition the sensitivity of the push-out behaviour regarding the different interface properties and the plastic flow curve of the tungsten fiber are investigated.

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Development of tungsten fibre-reinforced tungsten composites towards their use in DEMO—potassium doped tungsten wire

Cited by 89 publications

References 21 publications

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

Tungsten–potassium: a promising plasma-facing material

Insight into single-fiber push-out test of tungsten fiber-reinforced tungsten

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