On the role of twinning during room temperature deformation of γ-TiAl based alloys

The present work dealing with the micromechanical modeling of the deformation behavior of γ-TiAl based alloys is based on a strong interaction between numerical simulation facilities and detailed experimental investigations. Main attention is devoted to a near-γ microstructure which exhibits equiaxed γ-grains and α2-phase located at grain boundaries and triple junctions. The purpose is an investigation of the deformation mechanisms of polycrystalline near-γ material using both computational finite element simulations and acoustic emission (AE) measurements. A three-dimensional micromechanical model, initially developed to describe lamellar γ-TiAl, has been adjusted to simulate the deformation behavior of polycrystalline near-γ material. The contribution of deformation twinning to the total plastic deformation is computed investigating compression tests at room temperature. Concerning the onset of twinning the results of our simulation are compared with experimental data obtained from AE measurements. Investigations of the influence of various heat treatments on the twinning evolution during loading at room temperature were carried out. The deformation mechanisms were analyzed using optical microscopy, SEM and TEM.