Channelling of plastic deformation by interfaces in TiAl intermetallics

Plastic deformation in the lamellar microstructure of the L1(0) tetragonal phase is strongly affected by special rotational lamellar interfaces on the {111} close packed planes and by general grain boundaries separating the lamellar colonies. The activity of possible deformation modes in Ti-rich TiAl alloys is explained considering in addition to generally known asymmetry of deformation twinning the asymmetry of superdislocation motion. The restrictions imposed on the direction of propagating deformation by the lamellar interfaces are analysed in detail. Even in the case when the transfer of plastic deformation across the interfaces does not occur, the presence of interfaces as strong obstacles to moving dislocations and deformation twins can lead to localisation of strain parallel to the lamellae, to so called channelling of deformation. General grain boundaries can also significantly influence plastic deformation by stress redistribution due to the compatibility stresses arising from the crystal elastic anisotropy and from the anisotropy of plastic deformation.