Session J1 - Multiscale Modeling and Mechanical Properties.
FOCUS session, Tuesday afternoon, June 26
Building 10, Room 250,
Interactions of point defects (vacancies and interstitials) and dislocations play an important role in materials mechanical properties. In this paper, we employ the semidiscrete variational Peierls-Nabarro model to study the core properties of various dislocations in Al with and without point defects. In specific, the point defects we study in this paper are vacancy and interstitial H. The material parameters, including elastic constants and generalized stacking fault energy surfaces entering the model are calculated from ab initio approaches with large supercells to simulate the low concentration of vacancy and H interstitial (less than 5 at.properties, such as core energy, Peierls stress and core structure are calculated with and without the point defects and the interactions between them are thus revealed. We find although there is a strong binding between H interstitial and dislocation cores, a weak repulsion is observed for vacancy and dislocations. Moreover while the binding energy of H at dislocation cores increases from screw to edge dislocations, the repulsion between vacancy and dislocations remains almost the same for the various dislocations we studied. The critical stress to move a dislocation, Peierls stress, is calculated and we find that both vacancy and H interstitial can reduce the Peierls stress significantly, while the latter has a more dramatic effect (orders of magnitude), strongly supporting the H-enhanced local plasticity theory of H-embrittlement. For the static dislocation core structure, we find vacancy can facilitate dislocations to dissociate into two partials, with distances between them ranging from 5 to 11 Ådepending on the dislocation characters, while H interstitial can only increase the dislocation width but without any dissociation.