In lamellar TiAl, concerted deformation occurs in adjacent true-twin related variants (O/OT). When deformation takes place in a given variant, O, by activation of the slip system with highest shear stress, slip proceeds in the companion variant, OT, by operation of a slip system of the same family in mirror orientation, including the slip direction. Depending on load orientation, the latter system may not necessarily exhibit the highest resolved shear stress. The correlation does not depend upon Burgers vector orientation with respect to the interface.
This property applies to ordinary dislocations and twinning. The variant that conforms the Schmid law is referred to as the pilot variant, the twin-related variant is dubbed driven.