Recrystallization-mediated crack initiation in tungsten under simultaneous high-flux hydrogen plasma loads and high-cycle transient heating

Abstract Tungsten and tungsten-based alloys are the leading material choices for divertor plasma facing components (PFCs) in future fusion reactors. Recrystallization may occur when they undergo high heat loads, drastically modifying predesigned grain structures associated desired mechanical properties. However, influence of recrystallization on thermal fatigue behavior tungsten PFCs still remains unclear. In this study, ITER-grade was simultaneously exposed to a high-flux hydrogen (?5 × 10 24 m ?2 s ?1 ) high-cycle (10 4 –10 5 transient loads linear device Magnum-PSI. By correlating surface temperature distribution, obtained by analyzing temperature-, wavelength-, surface-dependent emissivity, modifications specimens, crack initiation flux factor threshold found be ?2 MW 0.5 (equivalently, ?0.07 MJ 1 ms pulse). Based electron backscatter diffraction analyses cross-sections near sites, faster kinetics compared literature observed cracks preferentially initiated at angle grains boundaries (HAGBs). Upon recrystallization, yield strength decreases which entails increasing cyclic plastic strains. The HAGBs fraction is increased, constrains transfer strains boundaries. dislocation density, promotes heterogeneous deformation. All these mechanisms explain reduced recrystallized its as-received counterpart. results provide new insights into structural failure extreme plasmas.