When 3:30 PM - 5:00 PM Oct 09, 2009
Where 1670 CSE
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Modeling Coupled Displacive-Diffusional Processes during Plastic Deformation and Phase Transformation

Yunzhi Wang, Ohio State University

Microstructural evolution in materials often involves coupled displacive and diffusional processes as a rule rather than as an exception. Consider for instance dislocation-precipitate interactions in Ni-base superalloys. Diffusive processes such as chemical reordering can couple strongly to dislocation shearing processes in governing the rate of deformation. On the other hand, dislocation plasticity can also change the precipitate microstructure in so-called directional coarsening or rafting process. Formation of new phases in many alloy systems involves lattice shear, shuffle, short-range and long range diffusion. Mechanistic studies of these mechano-chemically coupled processes require modeling capabilities at micrometer, nanometer and even atomistic length scales but diffusional time scales. In this presentation, recent efforts in developing multi-scale approaches by integrating ab initio calculations and atomistic simulations with continuum phase field method at all length scales will be reviewed. Examples will be given to demonstrate the quantitative aspects of the approach in (a) predicting defect size and energy, and thermally activated processes of defect nucleation and migration, utilizing directly ab initio information as model input, and (b) identifying and incorporating deformation and transformation mechanisms in combination with advanced experimental characterizations. 

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