Materials World Network: Collaborative Res.: Theoretical, Computational and Experimental Studies of 3D Microstructural Evolution in Ultra-high Volume Fraction Coarsening Systems

美国佛罗里达理工学院和宾夕法尼亚州立大学与德国德累斯顿的乌尔姆大学和工业大学合作，解决了相位粗化的根本问题。这个项目的主要目标是了解超高(90%)体积分数下的相粗化动力学，预计这将从根本上不同于在消失体积分数(~0%)下的经典Lifshitz/Slyosov/Wagner动力学，以及单相系统中的颗粒生长动力学(100%)。该团队进行了理论、计算和实验研究相结合的研究。具体的研究活动包括：(1)发展超高体积分数相粗化的新理论；(2)对复杂的三维(3D)微结构演化进行大规模相场模拟，将获得粗化率、颗粒尺寸分布和关联函数的时间演化等重要信息；(3)利用时间分辨X射线显微层析成像技术原位测量真实两相体系的三维粗化行为；以及(4)在理论、模拟和实验之间进行定量比较。对三维相粗化动力学的定量了解对于优化工艺条件以控制多相材料的最终组织和性能至关重要。粗化相的体积分数是决定粗化动力学的关键因素。由于粗化阶段高体积分数的复杂微观结构带来了巨大的理论和实验挑战，现有的理论工作仅限于低体积分数(~30%)，大多数实验表征都是通过金相切片在二维(2D)上进行的。然而，最近在理论建模、计算模拟和三维微结构表征方面的进展为克服超高体积分数粗化研究中固有的困难提供了前所未有的机会。因此，这个项目的具体推动力在于提高我们对基本材料现象的理解，发现与复杂微结构相关的新动力学，以及促进三维微结构演化和性质的模拟和实验工具的最新发展。参与这个项目的学生和初级研究人员前往大西洋对口的机构，以便沉浸在三维微结构演化的理论、计算和实验研究中。通过学生交换计划，这些年轻的研究人员受益于发展技能的机会，这些技能补充了他们在本国机构接受的理论、模拟或实验方面的强化培训，从而获得了多方面的教育体验。该奖项由美国国家科学基金会国际科学与工程办公室共同资助。

Florida Institute of Technology and Penn State University in the US team up with Ulm University and the Technical University in Dresden, Germany, to address the fundamental problem of phase coarsening. The primary goal of this project is to understand the kinetics of phase coarsening at ultra-high ( 90%) volume fractions, which are expected to be fundamentally different from the classical Lifshitz/Slyozov/Wagner kinetics at vanishing volume fractions (~0%) as well as from the kinetics of grain growth in single-phase systems (100%). The team conducts a combination of theoretical, computational and experimental studies. Specific research activities include: (1) developing a new theory for phase coarsening at ultra-high volume fractions; (2) conducting large-scale phase-field simulations of complex three-dimensional (3D) microstructural evolution that will yield important information such as coarsening rates, the temporal evolution of particle-size distributions and correlation functions, etc.; (3) measuring the 3D coarsening behavior of real two-phase systems in situ using time-resolved x-ray microtomography; and (4) carrying out quantitative comparisons between theory, simulation and experiments. A quantitative understanding of 3D phase coarsening kinetics is crucial to the optimization of processing conditions for controlling the final structure and properties of multiphase materials. The volume fraction of the coarsening phase is a critical factor in determining the coarsening kinetics. Due to the daunting theoretical and experimental challenges posed by complex microstructures at high-volume fractions of the coarsening phase, existing theoretical work has been limited to low volume fractions ( ~30%), and most experimental characterization has been carried out solely in two dimensions (2D) by metallographic sectioning. However, recent advances in theoretical modeling, computational simulation and 3D microstructural characterization offer an unprecedented opportunity to overcome the difficulties inherent in the study of coarsening at ultra-high volume fractions. The specific thrusts of this project therefore lie in improving our understanding of fundamental materials phenomena, in discovering new kinetics associated with complex microstructures, and in advancing the state of the art of simulation and experimental tools for 3D microstructural evolution and properties.Students and junior researchers participating in this project travel to the counterpart institutions across the Atlantic in order to immerse themselves in theoretical, computational and experimental studies of 3-D microstructural evolution. Via the student exchange program, these young researchers profit from the opportunity to develop skills that complement the intensive training in theory, simulation, or experiment that they receive at their home institutions, resulting in a multifaceted educational experience.This award is co-funded by the NSF Office of International Science and Engineering.