Neon-concentration dependent retarding effect on the recrystallization of irradiated tungsten: Experimental analysis and molecular dynamics simulation

Recrystallization is a critical issue in ITER and future fusion devices as it strongly deteriorates the properties and serving life of tungsten divertor armor. In this work, we investigated the influence of neon on the recrystallization behavior of tungsten and its underlying mechanism by both experimental analysis and molecular dynamics simulation. Rolled tungsten was irradiated by neon ion with energies of 10 and 100 keV and fluences of 1 × 10¹⁸–1 × 10²⁰ m⁻², followed by isochronal annealing at various temperatures (1473–2073 K) for 1 h. The results indicate that 10 keV neon ion irradiation slightly inhibits tungsten recrystallization due to the shallow depth distribution of neon (35 nm), whereas 100 keV neon ion irradiation exerts a significant retarding effect on tungsten recrystallization when neon concentration reaches ∼10² appm. Grain boundaries can hardly move with neon concentration reaching 400 appm, above which the retarding effect is very strong and varies little. The retarded recrystallization is mainly attributed to the pinning effect of neon clusters/bubbles on the grain boundary movement during annealing. Large neon clusters are found to play a predominant role in the retarding effect and the un-clustered neon atoms show a very limited effect on the grain boundary movement. By comparing the neon effects on recrystallization in this work and helium effects reported in the literature, we found that helium exhibits a relatively stronger recrystallization retarding effect than neon. This is because helium is more easily to diffuse into grain boundaries and form larger clusters due to its high diffusivity and low self-trapping energy in tungsten, which can greatly impede the migration of grain boundaries. This work provides a fundamental insight into the neon-concentration dependent recrystallization retarding effect in tungsten and the corresponding underlying atomic-level mechanisms.