Recrystallization at high temperature of two tungsten materials complying with the ITER specifications
Résumé
Estimating the lifetime of W-armoured divertor components is of great importance for ITER. During heat loading, one of the mechanisms inducing tungsten microstructure modification is recrystallization. As tungsten recrystallization induces a decrease of the mechanical properties, the knowledge of the recrystallization kinetics of the ITER tungsten material is necessary over the entire divertor PFU operational temperature window (up to 2000 °C). Some data exist for temperature loading lower than 1350 °C. For higher temperatures, some constraints due to the heating system and its impact on recrystallization process limit the possibility of high temperature studies. For this reason, in this study, a laser heating device and related diagnostics are used for the determination of the recrystallization kinetics. The Johnson Mehl-Avrami Kolmogorov (JMAK) equation is used to model the recrystallization process. Recrystallization kinetics for annealing temperatures higher than 1400 °C are provided for two tungsten materials produced according to the ITER specifications. At 1600 °C (resp. 1800 °C), recrystallization fraction of 50% is obtained after 200 s (resp. 10 s) thermal loading for one batch and after 500 s (resp. 50 s) for the other one.
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