Speaker
Description
In fusion reactors, the divertor fulfills two core functions: first, expelling impurities produced by plasma-first wall interactions and helium (a fusion product); second, withstanding high heat flux from the plasma and dissipating plasma energy out of the tokamak device. During operation, the divertor endures extreme thermal loads. As one of the most promising candidate materials for future divertors, tungsten (W) faces considerable challenges. Conventional powder metallurgy-derived tungsten suffers from low recrystallization temperature and high ductile-to-brittle transition temperature (DBTT), failing to meet the requirements for divertor base materials. In contrast, the novel rolled W-K alloy effectively increases recrystallization temperature, enhances mechanical properties, and reduces DBTT. Thermoplastic deformation further optimizes its mechanical performance and ductility while retaining tungsten’s inherent high thermal conductivity, endowing the W-K alloy with excellent comprehensive properties to cope with the harsh service environment of future fusion reactor divertor facing materials.
In this study, large-sized bulk W-K alloy was fabricated via hydrogen sintering, followed by hot rolling with a deformation degree of 60–80%. Tensile tests revealed that the alloy exhibited significant plastic deformation at 50°C, with tensile strain exceeding 5% and room-temperature tensile strength surpassing 1400 MPa. High-heat-flux test mock-ups of various sizes were prepared using the thermoplastically deformed W-K alloy, and tested under different loading conditions via the EMS-60 facility. Different tungsten blocks on the same mock-up underwent combined transient-steady-state tests with varying pulse durations and counts, as well as high-heat-flux tests simulating plasma disruption and vertical displacement events (VDEs). Subsequent systematic characterization of the test mock-ups’ surface morphology and crack depth showed that under combined transient-steady-state conditions, surface crack formation of W-K alloy samples was closely associated with the pulse count and duration of transient thermal loading. When the pulse duration was 0.1 ms, no obvious surface cracks were observed after 50,000 thermal shock cycles; however, when the pulse duration increased to 0.5 ms, a crack network formed on the surface after only 10,000 cycles. In tests simulating plasma disruption and VDEs, the area and morphology of the sample’s heat-affected zone changed significantly with increasing loading power. When obvious surface melting occurred, the W-K alloy samples exhibited distinct surface morphological differences compared to pure tungsten samples.