Nucleation and Growth of Solid-State Transformations

9806749Olson本研究项目以马氏体相变为例，研究一级固态相变的基本原理。理论和实验解决了多尺度微结构演化，利用非线性非局部模型来桥接长度尺度。将Landau-Ginsburg模型引入无单元伽辽金(EFG)方法，计算了在位错缺陷处形成的马氏体胚胎的三维结构，研究了形核前驱和共格转变。对于包括钢和形状记忆合金在内的重要技术体系的实际处理，FP-LMTO总能量电子计算解决了马氏体晶格变形的非线性能量学，以纳入连续统计算。将非局部塑性模型应用于塑性介质中的马氏体生长问题，作为模拟形态转变的基础。热弹性和非热弹性体系中的定量体视学测量定义了成核位、势分布和颗粒体积的演化。这些结合在一个包含形态转变的综合动力学模型中。在当前感兴趣的生物系统中，探索了马氏体理论与分子水平的蛋白质置换转变的相关性。%这个研究小组是美国工业用金属合金设计的领先活动。该方法是基本的，依赖于实验测量和理论。

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.***