A numerical model for the recrystallization kinetics of tungsten monoblocks under cyclic heat loads

Varun Shah, Hans van Dommelen*, Selwin Heijkoop, Mathieu Oude Vrielink, Marc Geers

*Bijbehorende auteur voor dit werk

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The recrystallization assisted microstructural changes during cyclic heat exposure are surmised detrimental to the thermal fatigue resistance of the tungsten monoblocks that cover the surface of the divertor components of a nuclear fusion reactor. A numerical framework to predict recrystallization in tungsten monoblocks during cyclic heat exposure is presented in this work. The framework is based on a thermal model coupled to a Johnson-Mehl-Avrami-Kolomogorov (JMAK) type recrystallization model. The influence of the initial (starting) microstructural state, i.e. the degree of deformation, on the extent of recrystallization, is considered through the activation energy for recrystallization. For a highly deformed microstructure, significantly more recrystallization is observed compared to self-diffusion driven recrystallization. The activation energy for recrystallization within the range 322 to 350 kJmol−1 during cyclic heat exposure of a monoblock is determined from the simulated recrystallization extent in relation to the experimental observations of differently processed monoblocks. The influence of the heating time per cycle for different activation energies on the recrystallization extent is also investigated. Instead of bulk recrystallization, only localized surface recrystallization is observed for a combination of a shorter heating time per cycle and a moderately deformed initial microstructure, which may contribute to improving the thermal fatigue resistance of the monoblocks.

Originele taal-2English
Artikelnummer112827
TijdschriftFusion Engineering and Design
Volume173
Vroegere onlinedatum17-aug-2021
DOI's
StatusE-pub ahead of print - 17-aug-2021
Extern gepubliceerdJa

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