Characterization of the Crack and Recrystallization of W/Cu Monoblocks of the Upper Divertor in EAST

Abstract

The microstructure of and damage to the upper divertor components in EAST were characterized by using metallography, EBSD, and SEM. Under the synergistic effect of heat load and plasma irradiation, cracking, recrystallization, and interface debonding were found in the components of the upper divertor target. The crack propagates downward from the heat loading surface along the heat flux direction, and the crack propagation mode is an intergranular fracture. The thermal loads deposited on the edge of monoblocks raise the temperature higher than the recrystallization temperature of pure tungsten, and the microstructure changes from being in a rolled state to being recrystallized. Additionally, cracks exist in both recrystallized and rolled areas. EBSD boundary maps show that the range of the recrystallization area is determined via the heat flux distribution. The Cu/CuCrZr interface of the cooling components near the thermal loading area is debonded, and the structural integrity is destroyed.

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“…Xiang Zan et al [53] have studied, by metallography and SEM+EBSD technique, the microstructure of the upper divertor components of EAST, consisted of the CuCrZr cooling components, protected by tungsten armor, that have been damaged because of the just mentioned melting failure event occurred during the 2019 campaign. The recrystallization of the rolled tungsten components has been observed and the range of the recrystallization had been determined via heat flux distribution.…”