Colony property determination in a gamma titanium aluminide

Gamma titanium aluminide (gamma-TiAl) alloys have been under development for use in rotating components for gas turbine engines. Detailed 3-dimensional (3D) colony-level finite element (FE) models are being developed at the U.S. Air Force Research Laboratory to predict damage initiation and accumulation in gamma-TiAl during service loading. These models require knowledge of the orthotropic nature of the deformation and fracture behavior of individual colonies. While the elastic properties of gamma and alpha-2 single-phase materials have been extensively studied, the elastic response of fully lamellar two-phase materials has not received the same degree of attention. This paper describes an integrated experimental and analytical approach to deduce the colony properties in a gamma-TiAl. Samples with gage sections composed of specifically-oriented individual lamellar grains were tested in tension to determine the elastic behavior of this two-phase structure. Preliminary 3D FE analysis, using the constituent properties available in the open literature, showed general agreement between the model results and the experimental measurements.