Abstract
In the present thesis, a thermomechanically coupled, defect density based crystal plasticity model is presented. This model accounts for the evolution of dislocation densities and twinned volume fractions on different slip and twinning systems during plastic deformation and thermal recovery. Considering the evolution of dislocation densities and twinned volume fractions allows a physics based formulation of the work hardening model and enables a physically meaningful representation of dissipation and stored energy of cold work in the applied thermomechanical framework. In the course of this thesis, the presented crystal plasticity model was applied to investigate several aspects of the plastic deformation behavior of fully lamellar titanium aluminide alloys. After calibrating the work hardening model to fit experimental results, it was successfully used to relate specifics of the macroscopic stress-strain response of fully lamellar titanium aluminides to the work hardening interactions on the microscale. By combining numerical studies and experimental findings from literature, it was further possible to identify and consequently model the relative contribution of the different coexisting microstructural interfaces to the macroscopic yield strength. With this microstructure sensitive model formulation, the influence of the microstructural parameters on the inhomogeneous microplasticity of fully lamellar titanium aluminides was studied. Due to its defect density based formulation, the model enabled trends in the static recovery behavior to be investigated. Finally, the model was extended in order to account for the anomalous dependence of the yield strength of fully lamellar titanium aluminides on temperature.
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