Plastic flow of γ-TiAl-based polysynthetically twinned crystals: micromechanical modeling and experimental validation

A micromechanical model for the calculation of the plastic behavior of a lamellar structure is presented. This model is based on a rate-sensitive approach to describe the plasticity at the single crystal (lamella) level and on the relaxed constraints theory to account for the influence of the lamellar morphology on the overall plastic response of the structure. The equations for the cases of 2- and N-lamellae structures undergoing states of applied stress or strain rate are presented. The model is applied to a lamellar matrix–twin pair which is a simplified representation of a γ-TiAl polysynthetically twinned (PST) crystal. For this case, a morphology-based classification of the critical stresses of the γ-TiAl deformation systems is also presented. This model for PST plasticity is successfully validated by comparison with available experimental data.