The generation of faulted dipoles and dislocation activity in γ-TiAl

Abstract

Faulted dipoles (FDs) nucleates at the tip of a <011] screw lock while the latter is unzipped by the connecting mixed segment. The transformation is favoured by the asymmetrical dissociation mode of the <011] dislocation, into two partials with 1/6<112] and 1/6<154] Burgers vectors bordering an intrinsic stacking fault. Where the parent <011] dislocation switches from a locked, 3D non planar to a fully coplanar core configuration at the connecting mixed segment, the 1/6<154] partial assumes a zonal form capable of expelling a partial dislocation with 1/6<112] Burgers vector. The latter transforms the fault from intrinsic to extrinsic and leaves a 1/3<121] partial with a zonal core on the other side of the fault. The presence of FDs reflects the propensity of <011] dislocations to form screw locks and thus attests to the operation of <011] dislocations during deformation.