Statistical Mechanics of Microstructural Evolution

小行星9633346 这项研究是针对发展一个坚实的实验基础和更深入地了解两相合金的微观结构演变。 重点是整合和测试几个理论，描述微观结构粗化动力学。 具体而言，“快照”计算，基于点源和汇的分布，以表示在稀微结构中的扩散相互作用，扩展到更高的体积分数。 二元合金的动力学研究被发现表现出时间指数在超致密的微观结构，奇怪的是，从经典的奥斯特瓦尔德成熟值的1/3的值为1/4。 这是由于尚未解释的动力学行为的影响，颗粒形状的住宿和强空间相关性。 总之，研究集中在理论和实验上的努力，整合和验证粗化理论的基本要素，以实现在体积分数范围0- 1的微观结构演变的更统一的动力学描述的进展。 该补助金的核心主题包括确定在整个组合物范围内加工的合金的动力学定律，并通过基本动力学原理对其进行解释。 金属合金的性能取决于其微观结构，而微观结构行为主要取决于时间、温度和成分。 温度控制原子扩散的速率，而在一个固定的温度下，平均化学组成决定了分散相的体积分数，并间接地建立了扩散和界面过程的微观结构长度尺度。 ***

9633346 Glicksman This study is directed toward developing a firm experimental basis and deeper understanding of microstructural evolution in two-phase alloys. The focus is to integrate and test several theories that describe microstructural coarsening kinetics. Specifically, "snap-shot" calculations, based on distributions of point sources and sinks to represent diffusional interactions in dilute microstructures, are extended to higher volume fractions. Kinetic studies on binary alloys are pursued which are found to exhibit temporal exponents in ultra-dense microstructures that, curiously, decrease from the classical Ostwald ripening value of 1/3 to a value of 1/4. This is attributed to an as yet unexplained kinetic behavior from the influence of particle shape accommodation and strong spatial correlations. In summary, the research focuses both theoretical and experimental efforts on integrating and validating fundamental elements of coarsening theory to achieve progress toward a more unified kinetic description of microstructure evolution over the volume fraction range 0- 1. %%% The core subjects of this grant include determining kinetic laws for alloys processed over the full range of compositions and explaining them through basic kinetic principles. Properties of metal alloys depend on their microstructure, and the microstructural behavior depends primarily on time, temperature, and composition. Temperature controls the rate of atom diffusion, whereas, at a fixed temperature, the average chemical composition determines the volume fraction of dispersed phases, and, indirectly, establishes the microstructural length scales for diffusion and interfacial processes. ***