Annihilation of interstitial-type dislocation loops in α-Fe during He irradiation

Interstitial-type dislocation loops were formed in Fe–9Cr alloys on irradiation with 1-MeV He ions at 673 K. However, with increasing irradiation dose, the dislocation loops shrunk. A molecular dynamics simulation was used to elucidate the mechanism of this unexpected phenomenon. The simulation shows that, although the binding energy of a self-interstitial atom to a dislocation loop is normally greater than that of a vacancy, the energy hierarchy is reversed when He atoms decorate the loop. This may indicates preferential absorption of vacancies, causing loop shrinkage at high doses, consistent with experimental observation.