Atomistic study of ordinary ½〈110] screw dislocations in single-phase and lamellar γ-TiAl

• Published in: Philosophical magazine (Abingdon, England) Vol. 87; no. 12; pp. 1795 - 1809
• Main Authors: Katzarov, Ivaylo Hristov, Cawkwell, Marc, Paxton, Anthony T, Finnis, Michael W
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 17-01-2007
• Subjects: Physical Sciences
• ISSN: 1478-6435; 1478-6433
• DOI: 10.1080/14786430601080252

Computer simulation of the core structure and glide of ordinary ½〈110] screw dislocations in single-phase L10 TiAl and in two lamellae forming twin γ/γ-interface has been performed using recently constructed Bond-Order Potentials (BOPs). BOPs represent a semi-empirical, numerically efficient scheme that works within the orthogonal tight-binding approximation and is able to capture the directionality of bonding. We have studied dislocation glide in perfect L10 TiAl and along a twin interface, transmission of an ordinary screw dislocation between lamellae, and the core structure, mobility and detachment of an interfacial ½〈110] screw dislocation from a twin boundary under applied shear stresses in directions parallel and perpendicular to a (111) plane. Our results show that the glide of ordinary ½〈110] straight screw dislocations under applied stresses in L10 TiAl is characterized by zigzag movement on two conjugated {111} planes. The non-planar core of the ½〈110] screw dislocation is distorted asymmetrically when the elastic center of the dislocation is close to a twin γ/γ-interface and the dislocation moves on one of the (111) planes, depending on the magnitude of the corresponding Schmid factor. Ordinary dislocations become ordinary interfacial dislocations when they reach the interface. With increasing applied stress they can glide into the adjacent lamella, leaving no remnant interfacial dislocation.