Nucleation and Growth of Solid-State Transformations

9806749奥尔森这个研究计划是针对一阶固态相变的原则，使用马氏体反应的原型情况。 理论和实验解决多尺度微观结构的演变，利用非线性非局部模型桥梁长度尺度。 Landau-Ginsburg模型被纳入无网格伽辽金（EFG）方法中，以计算在钢中位错缺陷处形成的马氏体胚的3D结构，研究成核前体和相干转变。 对于包括钢和形状记忆合金在内的技术重要系统的实际处理，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，以便纳入连续计算。 将非局部塑性模型应用于塑性介质中马氏体生长问题，作为模拟形态转变的基础。 在热弹性和非热弹性系统中的定量体视学测量定义了成核位点的势分布和颗粒体积的演变。 这些都结合在一个全面的动力学模型，将形态转变。 马氏体理论与分子水平蛋白质置换转换的相关性在当前感兴趣的生物系统中进行了探索。该研究小组是美国在设计工业应用金属合金方面的领先活动。 该方法是基础性的，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.***