title: Direct observation of interstitial dislocation loop coarsening in α-iron.
abstract: Interstitial loop coarsening by Ostwald ripening can provide insight into single point defects but is very difficult to observe in α-iron and many other metals where nanoscale vacancy clusters dissociate and annihilate loops. We show that by implanting helium in the samples at a carefully chosen energy, it is possible to observe Ostwald ripening of loops by transmission electron microscopy during in situ isochronal annealings. This coarsening of loops results in a sharp increase of the mean loop radius at around 850 K. Using cluster dynamics simulations, we demonstrate that loops evolve due to vacancy emission and that such experiments give a robust estimation of the sum of the formation and migration free energies of vacancies. In particular, our results are in good agreement with self-diffusion experiments and confirm that entropic contributions are large for the vacancy in α-iron.
authors.affiliation: CEA, DEN, Service de Recherches de Métallurgie Physique, F-91191 Gif-sur-Yvette, France.
authors.forename: S
authors.initials: S
authors.lastname: Moll
authors.forename: T
authors.initials: T
authors.lastname: Jourdan
authors.forename: H
authors.initials: H
authors.lastname: Lefaix-Jeuland