Recrystallization, a critical issue that weakens the strength and thermal shock resistance of tungsten-based plasma-facing material in fusion devices, is effectively retarded by helium. In this study, the retarding effect of helium on recrystallization was studied using tungsten samples implanted by high-dose helium ions with doses ranging from 5 × 1021m−2 to 1 × 1023 m−2 at two temperatures (room temperature and 673 K), and followed by annealing temperatures ranging from 1573 K to 2073 K. The results show that helium in all six samples exhibits retarding effect, with recrystallization beginning until 1773 K. Notably, the sample implanted at 673 K with a dose of 5 × 1021 m−2 demonstrates the lowest recrystallization fraction of 13% at the annealing temperature of 1873 K, suggesting that the retarding effect weakens once the helium ion concentration exceeds a certain threshold. The hardness of high-dose helium ion-implanted tungsten samples exhibits distinct temperature-dependent patterns, different from the monotonic decline typically observed in previous helium-implanted tungsten samples. Additionally, the recovery of pinholes, created by the rupture of helium bubble, on {100} planes was observed to be the slowest, explained through molecular dynamics simulations. This work offers valuable insights into maintaining the retarding effect on recrystallization by tuning helium concentration in tungsten.
This paper investigates how the concentration of helium ions in tungsten affects the material's recrystallization, which is crucial for maintaining the strength and thermal shock resistance of plasma-facing components in fusion devices. The study found that helium effectively retards recrystallization, but this effect weakens once the helium concentration exceeds a certain threshold.