This paper reports atomistic simulations of the interactions between the dominant lattice dislocations in γ-TiAl (ordinary screw ½<110] and <101] super-dislocations) with all three kinds of γ/γ-lamellar boundaries in polysynthetically twinned TiAl. The purpose of this study was to clarify the early stage of lamellar boundary controlled plastic deformation in polysynthetically twinned TiAl. The interatomic interactions in the simulations were described by a bond order potential for L10-TiAl which provides a proper quantum mechanical description of the bonding. The dislocation core geometries which the lattice produced in proximity to lamellar boundarie, and the way in which these cores were affected by the elastic and atomistic effects of dislocation-lamellar boundary interaction, were of interest. A study was made of the way in which the interfaces affected the activation of ordinary dislocation and super-dislocation slip inside the γ-lamellae and transfer of plastic deformation across lamellar boundaries. Three new phenomena were found in the atomic-scale plasticity of polysynthetically twinned TiAl; due particularly to the elastic and atomic mismatch associated with the 60° and 120° γ/γ-interfaces: (i) two new roles of the γ/γ-interfaces, i.e. decomposition of super-dislocations within 120° and 60° interfaces and subsequent detachment of a single ordinary dislocation and (ii) blocking of ordinary dislocations by 60° and 120° interfaces resulting in the emission of a twinning dislocation.

Atomistic Studies of Interactions between the Dominant Lattice Dislocations and γ/γ-Lamellar Boundaries in Lamellar γ-TiAl. I.H.Katzarov, A.T.Paxton: Acta Materialia, 2009, 57[11], 3349-66