The role of twinning during deformation of γ-TiAl based alloys

In the crystal-plastic description of the deformation behaviour of γ-TiAl-Intermetallics twinning appears as a mode of plastic deformation to take into consideration in addition to crystallographic slip. Our approach to describe the twinning mechanism based on a critical shear stress criterion in an analogous way to Schmid's law for crystallographic slip. This means that the shear stress on the twin plane, resolved in the twinning direction, is the driving force for the nucleation and growth of the twins. This paper investigates the importance of twinning as a deformation mechanism by using a micromechanical model based on the finite element method. Computational simulations investigating lamellar as well as so called near-γ-TiAl microstructures are carried out.