Prediction of high temperature deformation behavior of a γTiAl alloy using a temperature-sensitive crystal plasticity model

Kurzfassung

For predictive analyses of materials and structures made of multi-phase TiAl alloys, available numerical models need to be continuously enhanced. In the current progress of computational approaches, there is substantial lacking of physically motivated numerical models that are able to predict high temperature mechanical behavior of TiAl alloys. So far, crystal plasticity based micromechanical models have been proposed to predict the deformation behavior of TiAl alloys considering different microstructure. However, these models do not take any physics based arguments into account to capture the temperature sensitivity of the material. In the available models, the slip rates are inherently temperature insensitive, thus, the models are limited to room temperature investigations only. To overcome this limitation, in the present work we propose a temperature-sensitive crystal plasticity model to analyze the high temperature deformation behavior of multi-phase TiAl alloys. In this model, temperature sensitivity has been incorporated into the crystallographic slip rates as a function of temperature, activation energy, and the history of slip activation. This model was implemented in the classical crystal plasticity framework and has been verified for the fundamental deformation behavior of two-phase lamellar PST-TiAl as found in the literature. In the present work, we show that the proposed model is able to predict the yield anisotropy for both room and high temperature, as observed in the two-phase (α2+γ) PST-TiAl alloy under 0°, 45° and 90° lamellar orientation. We also predict a temperature-sensitive obstacle parameter for dislocations to explain the yield anomaly at 800°C for 0° oriented lamellae. Furthermore, strain rate sensitivity due to temperature variation has been predicted using this model, yielding good agreement with the experimental data. The proposed model shows huge prospect in the predictive analysis of high temperature mechanical behavior of TiAl alloys.