The knowledge of materials properties and their behavior at high temperatures is of crucial importance in many fields. For instance annealing phenomena occuring during the thermomechanical processing of materials, such as recrystallization, have long been recognized as being both of scientific interest and technological importance. Different methods are currently used to study annealing phenomena and submit metals to heat loads. In this work, we present the design and the development of a laser-based facility for annealing tests. This experimental setup enables studies at the laboratory scale with great flexibility to submit samples to various spatial and temporal heating profiles. Due to the possibility to have optical access to the sample, laser heating can be combined to several non-contact diagnostics such as infrared imaging to control and analyse the temperature gradients. As case study, we present a set of experiments performed to study the recrystallization kinetics of tungsten. We demonstrate that samples can be heated linearly with heating rate up to ∼2000 K/s, at temperatures above 2000K, for seconds or hours, with typical errors in the temperature measurement of around 1% that depend mainly on the determination of sample emissivity. Such studies are of crucial interest in the framework of nuclear fusion, since the ITER nuclear reactor will operate with a full-W divertor.
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 (rep. 1800 °C), recrystallization fraction of 50% is obtained after 200 s (rep. 50 s) thermal loading for one batch and after 500 s (rep. 10 s) for the other one.
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