Behaviors of full compositional W/Cu functionally gradient materials exposed to the edge plasma of HT-7 tokamak

To investigate the behaviors of graded structure materials under plasma loading, six-layered W/Cu functionally gradient materials (FGMs) with full compositional distributions (from 0% to 100%) were successfully fabricated by resistance sintering under ultra-high pressure (RSUHP) method and were exposed to the edge plasma of the HT-7 tokamak. After about 210 shots plasma loading with an estimated power density in the range of 2–7 MW/m2, there is no detaching found at the graded interface corners where the thermal stress concentration is expected and the fatigue failures often occur initially, however, the brittle W layer develops the macroscopic cracks which can extend deeply into the interface and results in the interface failure or even the exfoliated W layer. To avoid these destructions for W/Cu FGMs during wall application, it is necessary to ameliorate the W layer by optimizing the initial powders and sintering parameters.