Possibility of (11(1)over-bar)(TB) accommodation mechanism for type-I twinintersection in gamma-TiAl during room-temperature deformation

Three intersection mechanisms with the gliding planes (11(1) over bar)(TB), (001)(TB) and (11(5) over bar)(TB) respectively have been observed by high -resolution electron microscopy in, the type-I twin intersection of gamma - TiAl. It was found that the intersection mechanism that occurred was relate d to the thickness of the incident twin. The accommodation mechanism on the (11(1) over bar)(TB) atomic;plane is preferred when the incident twin beco mes very thin. The dislocation dissociations of the (11(1) over bar)(TB) pl ane accommodation are the most energetically unfavourable of the dissociati ons of the three intersection mechanisms; however, the resultant dislocatio ns on the (11(1) over bar)(TB) planes are the easiest to propagate away fro m the intersection area. Accordingly, (11(1) over bar)(TB) atomic plane acc ommodation is considered to be the only mechanism allowing shear transmissi on under the small local stress of the pile-up of the incident twinning par tials.