A study was made of the crystallography of twinning in the ordered L10 structure of the γ-phase, and the resultant deformation was quantified for various crystallographic directions. It was also questioned whether twin interfaces were obstacles to glide dislocations. It was shown that one part of the possible glide dislocations remained unaffected by the twin interface because the Burgers vectors lay in the twin plane. The other part of the dislocation had to change its glide direction while passing the interface, which could occur via a suitable dissociation processes. One requirement was a sufficiently high applied stress. The reoriented twin could happen to be more favourably oriented, for some glide directions, than was its parent crystal. This then promoted further dislocation plasticity. The effect of this effect upon the ductility depended upon the twin volume fraction.

Crystallographic Aspects of Deformation Twinning and Consequences for Plastic Deformation Processes in γ-TiAl. B.Skrotzki: Acta Materialia, 2000, 48[4], 851-62