title: Dislocation locking versus easy glide in titanium and zirconium.
abstract: The ease of a metal to deform plastically in selected crystallographic planes depends on the core structure of its dislocations. As the latter is controlled by electronic interactions, metals with the same valence electron configuration usually exhibit a similar plastic behaviour. For this reason, titanium and zirconium, two transition metals of technological importance from the same column of the periodic table, have so far been assumed to deform in a similar fashion. However, we show here, using in situ transmission electron microscopy straining experiments, that plasticity proceeds very differently in these two metals, being intermittent in Ti and continuous in Zr. This observation is rationalized using first-principles calculations, which reveal that, in both metals, dislocations may adopt the same set of different cores that are either glissile or sessile. An inversion of stability of these cores between Zr and Ti is shown to be at the origin of the profoundly different plastic behaviours.
authors.affiliation: CEA, DEN, Service de Recherches de Métallurgie Physique, F-91191 Gif-sur-Yvette, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Clouet
authors.affiliation: CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347 F-31055 Toulouse Cedex, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Caillard
authors.affiliation: CEA, DEN, Service de Recherches de Métallurgie Physique, F-91191 Gif-sur-Yvette, France.
authors.forename: Nermine
authors.initials: N
authors.lastname: Chaari
authors.affiliation: CEA, DEN, Service de Recherches Métallurgiques Appliquées, F-91191 Gif-sur-Yvette, France.
authors.forename: Fabien
authors.initials: F
authors.lastname: Onimus
authors.affiliation: Institut Lumière Matière, Université Lyon 1, CNRS, UMR 5306, F-69622 Villeurbanne, France.
authors.forename: David
authors.initials: D
authors.lastname: Rodney