In this work, the creep deformation (rate) of creep exposed martensitic steel is modelled on a microstructural basis. This approach is chosen since microstructural models can be double checked with experimental findings of the microstructural evolution - as opposed to phenomenological models, where the only measurable output is the actual deformation. Thus, microstructural models can be tested in more detail.
The model considers the relevant microstructural constituents contributing to the deformation; in our case different kinds of precipitates, dislocations and matrix boundaries. These features are coupled by a mean field approach in order to guarantee good statistical significance. The model is then based on two concepts. First, the precipitate evolution is calculated by maximum energy dissipation within a multi-component, multi- precipitate environment. Second, dislocation densities and grain sizes are handled by concepts stemming from Ghoniem et al., with considerable improvements on a number of interactions. The results are tested against creep data, measurements of dislocation densities via XRD and TEM and grain sizes from EBSD.
The results of the model show good agreement to the experimental data. Once the few remaining fit parameters have been set according to the
comparison with a single creep-curve, the same parameters are fully applicable to a wide range of stresses and, in parts, also temperatures. As second reference, the modelled microstructural evolution coincides well with the experimental findings.
Once the model has been set up, it becomes a powerful tool for representing the evolution of the material group during creep and is applicable to a wide range of stresses. Due to the statistical representation of the microsructure, the model is extremely fast with some seconds calulation time per creep curve. The model can be considered almost complete with respect to the underlying mechanisms, few remaining gaps can be clearly identified and addressed to future work.
|Period||4 Sept 2019|
|Event title||European Congress and Exhibition on Advanced Materials and Processes: EUROMAT 2019|
|Degree of Recognition||International|
ASJC Scopus subject areas
- Materials Science(all)