Interaction of deformation twin and 120 deg-rotational order fault domain boundary in the lamellar structure of two-phase TiAl-based alloys

Abstract

Interactions between deformation twin and 120 deg-rotational domain boundary were studied by transmission electron microscopy in a two-phase TiAl-based alloy with fully lamellar structure deformed at room temperature. Three types of the interaction were observed, depending on the interaction geometry and crystallography faced by the incident twinning Shockleys. It was found that the incident twinning shear could be accommodated into the barrier domain by a reaction involving emission of 1/2 $\left. {\left\langle {1\bar 10} \right.} \right]_B$ {111} _B slip in all the three types of interactions presumably since the slip required a small critical resolved shear stress (CRSS) and was always favored by the pile-up stress. Several reaction schemes involving 1/2 $\left. {\left\langle {1\bar 10} \right.} \right]_B$ {111} _B slip for each type of the interactions were proposed by considering whether the reaction resulted in a reduced elastic energy and if the dissociated dislocations were able to glide away to minimize the total elastic energy associated with a long-range stress field of a pileup of the incident twinning partials. It is suggested that whether a reaction scheme is feasible would depend on behavior of other product dislocation except 1/2 $\left. {\left\langle {1\bar 10} \right.} \right]_B$ {111} _B .