Interaction of oxygen interstitials with lattice faults in Ti

Oxygen greatly affects the mechanical properties of titanium. In addition, dislocations and twin boundaries influence the plastics deformation of hexagonal close-packed metals. As part of a systematic study of defects interactions in Ti, we investigate the interactions of oxygen with (101̄2) twin boundaries and (101̄0) prism plane stacking faults. The energetics of four interstitial sites in the twin geometry are compared with the bulk octahedral site. We show that two of these sites located at the twin boundary are more attractive to oxygen than bulk, while the sites away from the boundary are repulsive. Moreover, we study the interaction of oxygen with the prismatic stacking fault to approximate oxygen-dislocation interaction. We show that oxygen increases the stacking fault energy and therefore is repelled by the faulted geometry and consequently a dislocation core.