Manufacturing of tungsten and tungsten composites for fusion application via different routes

Wu, Yucheng

doi:10.1007/s42864-019-00011-y

Cited by 33 publications

(13 citation statements)

References 100 publications

(116 reference statements)

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“…Notably, there are some dark gray discontinuous grains observed from these fracture morphologies, which are attributed to the Cr-rich phase. From the previous work [17], the SA powder was completely alloyed and with homogeneous microstructure after milling 60 h. Therefore, the Cr-rich phase could be possibly formed during the FAST densification process. The sintering peak-temperature of SA sample (1150 °C) is below its solution temperature (~ 1556 °C for W-11.4wt.%Cr) [18].…”

Section: Resultsmentioning

confidence: 99%

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Self-passivating smart tungsten alloys for DEMO: a progress in joining and upscale for a first wall mockup

et al. 2021

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Self-passivating, so-called smart alloys are under development for a future fusion power plant. These alloys containing tungsten, chromium and yttrium must possess an acceptable plasma performance during a regular plasma operation of a power plant and demonstrate the suppression of non-desirable oxidation of tungsten in case of an accident. The up-scaling of the bulk smart alloys to the reactor-relevant sizes has begun and the first samples with a diameter of 50 mm and thickness of 5 mm became available. The samples feature high relative density of above 99% and good homogeneity. With production of bulk samples, the research program on joining the smart alloy to the structural material was initiated. In a present study, the novel titanium–zirconium–beryllium braze was applied successfully to join the smart alloy to the Rusfer-reduced-activation steel. The braze has survived at least a hundred of cyclic thermal excursions in the range of 300–600 °C without mechanical destruction.

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Section: Resultsmentioning

confidence: 99%

“…It indicates that the SA bulk samples cannot be densified further. The slight increase in displacement curve is mainly due to the expansion of the graphite punch [17]. The corresponding temperature at the inflection point was called the densification temperature (marked with a red dot), which is the displayed temperature.…”

Section: Resultsmentioning

confidence: 99%

Self-passivating smart tungsten alloys for DEMO: a progress in joining and upscale for a first wall mockup

et al. 2021

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“…In recent studies [5][6][7][8], different kinds of dispersionstrengthened tungsten materials processed by hot-plastic deformation have been developed. The obtained samples have fine grains and improved performances.…”

Section: Introductionmentioning

confidence: 99%

Irradiation effects of H/He neutral beam on different forged tungsten materials

et al. 2019

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Tungsten has been considered as the most promising plasma-facing materials (PFMs) for the future fusion reactor due to its excellent chemical and physical properties. In this work, different kinds of tungsten-based PFMs including pure W, W-K, and W-Y 2 O 3 alloys were prepared via powder metallurgy. Then, high-energy rate forging was used for the plastic deformation to refine the grain size of the samples and increase their densities. To evaluate the service performance of these tungstenbased PFMs under edge plasma conditions, the deformed samples were exposed to high-energy hydrogen (H) neutral beam doped with 6 at% helium (He). Sequentially, edge-localized mode-like transient loadings (1 ms, 100 cycles) were carried out on the specimens with neutral beam pre-loading to study the impact of H/He pre-loading on the generation and propagation of cracks. The microstructural changes of the exposed surfaces were observed by scanning electron microscopy with the help of focused ion beam. The experimental results indicate that H/He neutral beam irradiation could induce obvious surface damages of the tested samples. For example, pinhole and coral-like nanostructures were formed on the surfaces of the exposed samples, as the surface temperatures were relatively high. The cracking thresholds of the W-Y 2 O 3 samples with and without neutral beam pre-irradiations were both between 0.22 and 0.33 GW m −2 , while the cracking thresholds of pure W and W-K samples were less than 0.22 GW m −2. This result indicates that the H/He neutral beam pre-loading has no significant impact on the cracking threshold. In addition, the crack pattern on the surface of the exposed samples closely depends on the grain boundary pattern.

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“…Furthermore, tungsten also exhibits certain intrinsic brittleness at low temperatures and reduction of mechanical properties due to recrystallization at high temperatures, which may lead to poor thermal shock resistance during thermal cycling [1]. From this point of view, small grain size, high purity, and good strength of the grain boundaries are generally beneficial [3]. Fine grains are also helpful for irradiation resistance, as the grain boundaries act as sinks to irradiation-induced defects [4].…”

Section: Introductionmentioning

confidence: 99%

On the Structural and Chemical Homogeneity of Spark Plasma Sintered Tungsten

Matějíček

Vilémová

Veverka

et al. 2019

Metals

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Tungsten-based materials are the prime candidate plasma-facing materials for future fusion reactors, such as DEMO. Spark plasma sintering is a prospective fabrication technology with several advantageous features. The concurrent application of electric current, temperature and pressure enhances the sintering process, allowing for lower temperatures and shorter sintering times than traditional powder metallurgy processes. This in turn helps to avoid excessive grain growth and phase segregation in W-alloys. This study is focused on several factors that may influence the homogeneity of the sintered compacts-namely the diffusion of carbon from the graphite die, purity of the powder and sintering conditions. The following characteristics of spark plasma-sintered tungsten compacts were studied: composition (especially carbon and oxygen content), porosity, mechanical properties (hardness and fracture strength), and thermal diffusivity. The effects of the abovementioned processing factors were quantified, and local variations of selected properties were assessed. plasma sintering (SPS, also called Field Assisted Sintering Technology, FAST) is a progressive technique to consolidate various materials, metals as well as ceramics, glass etc. Relatively low temperatures, high heating rates and short processing times-compared to traditional sintering techniques-are generally favorable for the retention of fine grains. In SPS, the sintered material in the form of powder is introduced into a die and, subsequently, high-intensity (pulsed or steady) electric currents up to several thousand A and uniaxial pressure up to hundreds MPa are applied. The die and the powder are heated by Joule heating. Graphite foil is usually inserted between the powder and the die in order to eliminate undesirable bonding of sintered material to the die. Depending on the parameters and the sintered material, temperature can reach up to~2400 • C and with suitable parameters, fully dense samples can be obtained [5][6][7]. Sintering parameters have a considerable effect on the resulting microstructure, homogeneity and other properties of the samples. Basic variables characterizing the sintering process are: (i) sintering temperature, (ii) applied pressure, and (iii) duration of the holding time at the sintering temperature. The results are also sensitive to the heating rate, manner of pressure application, die dimensions, sintering atmosphere etc.

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Manufacturing of tungsten and tungsten composites for fusion application via different routes

Cited by 33 publications

References 100 publications

Self-passivating smart tungsten alloys for DEMO: a progress in joining and upscale for a first wall mockup

Self-passivating smart tungsten alloys for DEMO: a progress in joining and upscale for a first wall mockup

Irradiation effects of H/He neutral beam on different forged tungsten materials

On the Structural and Chemical Homogeneity of Spark Plasma Sintered Tungsten

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