Possibility of (111) [sub TB] accommodation mechanism for type-I twin intersection in γ-TiAl during roomtemperature deformation.

Three intersection mechanisms with the gliding planes (111)[sub TB], (001)[sub TB] and (115)[sub 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 related to the thickness of the incident twin. The accommodation mechanism on the (111)[sub TB] atomic plane is preferred when the incident twin becomes very thin. The dislocation dissociations of the (111)[sub TB] plane accommodation are the most energetically unfavourable of the dissociations of the three intersection mechanisms; however, the resultant dislocations on the (111)[sub TB] planes are the easiest to propagate away from the intersection area. Accordingly, (111)[sub TB] atomic plane accommodation is considered to be the only mechanism allowing shear transmission under the small local stress of the pile-up of the incident twinning partials. [ABSTRACT FROM AUTHOR]