The impact of transient heat flux on tungsten fiber-reinforced tungsten materials

Tungsten fiber-reinforced tungsten materials (W_f/W_m), as an emerging plasma-facing material, hold promise in addressing the brittleness issues associated with traditional tungsten materials. However, the impact of transient thermal loads in nuclear fusion reactors, particularly on the tungsten fibers and interfacial structures, has been less studied, which hampers the further application and development of these materials. This paper simulates Edge Localized Modes (ELMs) events using an EMS-60 electron beam facility to subject W_f/W_m to transient thermal shock and compares the changes in fibers and interfaces before and after the transient thermal shock. The following conclusions are drawn: (1) Compared to pure tungsten materials,W_f/W_m exhibit superior performance under transient thermal loads. (2) Although in this study, the tungsten fibers and interfaces, when directly exposed to high thermal loads, can still effectively prevent crack propagation, they both experience significant performance degradation and loss of integrity. We infer that if the number of thermal shock cycles is further increased, the likelihood of failure of the fibers and interfaces may be significantly enhanced. Therefore, special attention should be paid to the failure of W_f/W_m caused by plasma flux in practical applications. (3) Tungsten fibers have an excellent inhibitory effect on cracks along the heat flux direction, and their ideal arrangement is beneath the material surface, at a position hundreds of micrometers away from the surface, where the fibers and interfacial structures can be preserved intact, effectively impeding crack propagation.