Computer simulation of the core structure and glide of ordinary ½<110] screw dislocations in single-phase L10 TiAl and in two lamellae forming a twin γ/γ-interface was performed using recently constructed bond-order potentials. The bond-order potentials represented a semi-empirical numerically efficient scheme that worked within the orthogonal tight-binding approximation and was able to capture the directionality of bonding. A study was made of 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. The results showed that the glide of ordinary ½<110] straight screw dislocations under applied stresses in L10 TiAl was characterized by zigzag movement on two conjugated {111} planes. The non-planar core of the ½<110] screw dislocation was distorted asymmetrically when the elastic center of the dislocation was 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 became ordinary interfacial dislocations when they reach the interface. With increasing applied stress they could glide into the adjacent lamella, leaving no remnant interfacial dislocation.

Atomistic Study of Ordinary ½ <110] Screw Dislocations in Single-Phase and Lamellar Gamma-TiAl. I.H.Katzarov, M.J.Cawkwell, A.T.Paxton, M.W.Finnis: Philosophical Magazine, 2007, 87[12], 1795-1809