PLASTIC-FLOW OF GAMMA-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-sens itive approach to describe the plasticity at the single crystal (lamel la) level and on the relaxed constraints theory to account for the inf luence of the lamellar morphology on the overall plastic response of t he structure. The equations for the cases of 2- and N-lamellae structu res undergoing states of applied stress or strain rate are presented. The model is applied to a lamellar matrix-twin pair which is a simplif ied representation of a gamma-TiAl polysynthetically twinned (PST) cry stal. For this case, a morphology-based classification of the critical stresses of the gamma-TiAl deformation systems is also presented. Thi s model for PST plasticity is successfully validated by comparison wit h available experimental data. (C) 1998 Acta Metallurgica Inc. Publish ed by Elsevier Science Ltd. All right reserved.