ATOMISTIC STUDIES OF 〈101] SCREW DISLOCATION CORE STRUCTURES AND GLIDE IN γ-TiAl

Ivaylo Hristov Katzarov (1) , Anthony T Paxton (1)

1 School of Mathematics and Physics

This paper focuses on the core structure of <101] superdislocations in L1₀ TiAl with the purpose of clarifying their dissociation abilities and the mechanisms by which these may become sessile by self-locking. A detailed knowledge of the fine structure of dislocations is essential in analysing the origin of the various deformation features. Atomistic simulation of the core structure and glide of the screw <101] superdislocation has been made using a Bond-Order Potential for γ-TiAl. We have examined the core structure of the screw <101] superdislocation starting with initial unrelaxed configurations corresponding to various dislocation dissociations, discussed in the literature. The superdislocation was found to possess in the screw orientation either planar (glissile) or non-planar (sessile) core structures. We studied the response of our core configurations to externally applied shear stress. We considered some implications of the dissociated configurations and their response to externally applied stress on dislocation dynamics, including the issue of dislocation decomposition, the mechanism of locking and the orientation dependence of the dislocation substructure observed in single-phase γ-TiAl. We find an unexpectedly rich and complex set of candidate core structures both planar and non-planar, whose cores may transform under applied stress with consequent violation of Scmid's law.

Mots clés: Physical Sciences

Ivaylo Hristov Katzarov, Anthony T Paxton. ATOMISTIC STUDIES OF 〈101] SCREW DISLOCATION CORE STRUCTURES AND GLIDE IN γ-TiAl. Philosophical Magazine, 2009, 89 (21), pp.1731-1750. ⟨10.1080/14786430903037281⟩. ⟨hal-00514030⟩