Molecular dynamics investigation of deformation twinning in γ-TiAl sheared along the pseudo-twinning direction Original Research Article

In spite of being sheared along the so-called pseudo-twinning image direction, γ-TiAl undergoes true twinning under zero pressure or hydrostatic tension by means of a specific combination of image, image and image shears in two consecutive (1 1 1) matrix planes allowing the adjacent twin to thicken over one (1 1 1) atomic layer. The corresponding total shear strain of image is four times as large as that generated by conventional deformation twinning or during the L10 to L11 transformation by image or image shears, respectively. This shear is substantially more effective in accommodating stress concentration and high strain rate than conventional deformation twinning. The conditions under which twinning by image dislocations operates are interpreted based on a modified gamma-surface and discussed in terms of zonal partial dislocations.