Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

Yuan, Ye; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, Guang–Nan; Xu, Heng; Fu, Baoqin; Li, M.; Liu, W.

doi:10.1016/j.jnucmat.2012.04.022

Cited by 53 publications

(27 citation statements)

References 14 publications

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“…1(a)). The sample installation and the design of cooling structure are consistent with our pervious study [8]. The sample surface is perpendicular to the beam axis.…”

Section: Methodssupporting

confidence: 76%

Surface modification of molten W exposed to high heat flux helium neutral beams

Yuan

Greuner

Böswirth

et al. 2013

Journal of Nuclear Materials

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High heat flux tests with central heat flux of 10.5 MW/m 2 using helium neutral beams have been carried out on rolled tungsten. The energy of helium particles is 33 keV and the particle flux is 2×10 21 m -2 s -1 . An 80×65×3 mm 3 rolled tungsten plate is firstly exposed to a 4.6 s pulse resulting in partially molten surfaces. Thereafter the tungsten plate is irradiated by several helium pulses with fluences of 1.2-2.5×10 22 /m 2 and peak temperatures from 1450 to 2590 °C . The experiments show that: (1) helium-induced surface modification of the resolidified tungsten surface is very different from that of the non-molten surface; (2) the surface morphology of molten surface is closely related to the orientation of the resolidified grain; (3) the evolution of surface modifications, for both of the molten and non-molten tungsten surfaces, 2 indicates a strong dependence on the surface temperature and local helium fluence.

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“…1(a)). The sample installation and the design of cooling structure are consistent with our pervious study [8]. The sample surface is perpendicular to the beam axis.…”

Section: Methodssupporting

confidence: 76%

Surface modification of molten W exposed to high heat flux helium neutral beams

Yuan

Greuner

Böswirth

et al. 2013

Journal of Nuclear Materials

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“…Such a higher value is in reasonable agreement with the activation energy of bulk self-diffusion 502-628 kJ/mol [15] and other observations in literature obtaining comparably high activation energies for recrystallization: For example, an activation energy of 544 kJ/mol is reported for recrystallization of an extruded rod of high purity tungsten [16], whereas for recrystallization of heavilydrawn wires activation energies of 502 kJ/mol and 573 kJ/mol are found when annealed under vacuum or Argon atmosphere respectively [17]. Lower values (closer to 352 kJ/mol) are less frequently reported; for instance, an activation energy of 396 kJ/mol has been found for grain growth after recrystallization of a similar plate warm-rolled to 75% thickness reduction [18].…”

Section: Discussionmentioning

confidence: 99%

Thermal stability of a highly-deformed warm-rolled tungsten plate in the temperature range 1100–1250 °C

Alfonso

Jensen

Luo

et al. 2015

Fusion Engineering and Design

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Pure tungsten is considered as armor material for the most critical parts of fusion reactors (i.e. the divertor and the first wall), among other reasons due to its high melting point (3422 °C) and recrystallization temperature. The thermal stability of a pure tungsten plate warm-rolled to a high plastic strain by 90% thickness reduction was investigated by isothermal annealing for up to 190 h in the temperature range between 1100 °C and 1250 °C. Vickers hardness testing allowed tracking the changes in mechanical properties caused by recovery and recrystallization. The hardness evolution could be rationalized in terms of a logarithmic recovery kinetics and a Johnson-Mehl-Avrami-Kolmogorov recrystallization kinetics accounting for an incubation time of recrystallization. The observed time spans for recrystallization and the corresponding recrystallization activation energy for this highly deformed plate suggest that large plastic deformations (e.g. applied during shaping) are only suitable to produce tungsten components to be used at relatively low temperatures (up to 900 °C for a 2 years lifespan). Higher operation temperatures will lead to fast degradation of the microstructure during operation.

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“…The He beam in this facility generates homogeneous heating due to the nearly complete absorption of the beam power on the W surface [9]. Although the sample holder is water cooled, due to poor thermal contact cooling of the W after each pulse is assumed to take place mainly by thermal radiation [1]. Surface temperatures were measured with pyrometers and with an IR camera.…”

Section: Methodsmentioning

confidence: 99%

“…Further details about the surface temperature measurements can be found in Ref. [1]. An example plot of surface temperature vs. time for 5 s heating is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

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Effects of temperature on surface modification of W exposed to He particles

Greuner

Yuan

et al. 2014

Journal of Nuclear Materials

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The effect of combined heating and helium particle flux on annealed tungsten samples has been studied in the neutral beam facility GLADIS. He beams with power densities of 2.4 MW/m 2 and 9.5 MW/m 2 were used to adiabatically load the samples to peak surface temperatures from ~ 950 °C (1223 K) to ~ 2700 °C (2973 K). Changes in the surface morphology resulting from combined heat and the flux exposure were studied for He fluences up to 3×10 22 /m 2 . Typical structures for the sample loaded at ~ 950 °C (1223 K) were blisters with a clear grain orientation dependence and the largest blisters formed on grains with <001> surface normal. However at higher temperatures, blistering was more easily suppressed for grains near this orientation because the growth of larger blister takes place more slowly. An evolution from a "porous structure" to a "coral-like structure" with increasing fluence was observed on the samples loaded at the highest temperature. Based on these results mechanisms for surface modification at different temperatures are discussed and a texture with <001> parallel to the normal direction of the grains is suggested to optimize the plasma facing material due to their stronger resistance to early stage blistering.

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Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

Cited by 53 publications

References 14 publications

Surface modification of molten W exposed to high heat flux helium neutral beams

Surface modification of molten W exposed to high heat flux helium neutral beams

Thermal stability of a highly-deformed warm-rolled tungsten plate in the temperature range 1100–1250 °C

Effects of temperature on surface modification of W exposed to He particles

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