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

Interactions between deformation twin and 120 deg-rotational domain boundar y were studied by transmission electron microscopy in a two-phase TiAl-base d alloy with fully lamellar structure deformed at room temperature, Three t ypes of the interaction were observed, depending on the interaction geometr y and crystallography faced by the incident twinning Shockleys. It was foun d that the incident twinning shear could be accommodated into the barrier d omain by a reaction involving emission of 1/2 [ 1 (1) over bar0](B) {111}(B ) slip in all the three types of interactions presumably since the slip req uired a small critical resolved shear stress (CRSS) and was always favored by the pile-up stress. Several reaction schemes involving 1/2 [ 1 (1) over bar0](B) {111}(B) slip for each type of the interactions were proposed by c onsidering 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 th e incident twinning partials, It is suggested that whether a reaction schem e is feasible would depend on behavior of other product dislocation except 1/2 [ 1 (1) over bar0](B) {111}(B).