Place: MINES ParisTech, Paris, France
Full field simulations of microstructure evolution under uniaxial tension in the high temperature low stress creep regime are presented. Creep in the disordered γ matrix and the ordered γ’ precipitates is treated using a phenomenological crystal plasticity model. Microstructure evolution is treated using a mesoscopic phase-field model. Special emphasis is given to the state of coherency between matrix and precipitates where a new model considers effective misfit dislocations based on the hardening parameters, and thereby the effective dislocation density in the crystal plasticity model. It is demonstrated that coalescence of individual precipitates which is an important mechanism for the onset of rafting, depends critically on the state of coherency. Further-on the role of slowly diffusing elements, like Re, on the rafting kinetics is investigated. The simulations are calibrated and compared to experimental creep tests. The calibrated model is applied to different loading conditions and alloy compositions. The mutual effect of chemo-mechanical coupling is highlighted.