Nucleation and Growth of Solid-State Transformations

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9806749OlsonThis research program is directed toward principles of first-order solid-state phase transformations using the prototypical case of martensitic reactions. Theory and experiment address multiscale microstructural evolution, exploiting nonlinear nonlocal models to bridge length scales. Landau-Ginsburg models are incorporated within an Element-Free Galerkin (EFG) method to compute 3D structures of martensitic embryos forming at dislocation defects in steels, investigating nucleation precursors and coherency transitions. For realistic treatment of technologically important systems including steels and shape memory alloys, FP-LMTO total energy electronic calculations address the nonlinear energetics of martensitic lattice deformations for incorporation in the continuum calculations. Nonlocal plasticity models are applied to the problem of martensitic growth in plastic media, as the basis of modeling morphological transitions. Quantitative stereological measurements in thermoelastic and non-thermoelastic systems define nucleation site potency distributions and the evolution of particle volume. These are combined in a comprehensive kinetic model incorporating morphological transitions. The relevance of martensite theory to molecular level protein displacive transformations is explored in biological systems of current interest.%%%This research group is the leading activity in the United States in designing metal alloys for application in industry. The approach is fundamental and relies on both experimental measurements and theory.***