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乌尔姆大学和德国德累斯顿工业大学合作，解决相粗化的基本问题。该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，这与消失体积分数（~0%）时的经典Lifshitz/Slyozov/Wagner动力学以及单相系统（100%）的晶粒生长动力学有本质的不同。该团队进行了理论、计算和实验研究的结合。具体研究工作包括：(1)建立超高体积分数相粗化新理论；(2)对复杂的三维（3D）微观结构演变进行大规模相场模拟，将获得诸如粗化率、粒度分布的时间演变和相关函数等重要信息；(3)利用时间分辨x射线微层析成像技术原位测量实际两相体系的三维粗化行为；(4)对理论、仿真和实验进行定量比较。三维相粗化动力学的定量理解对于控制多相材料的最终结构和性能的加工条件优化至关重要。粗化相的体积分数是决定粗化动力学的关键因素。由于粗化相大体积分数复杂的微观结构所带来的巨大理论和实验挑战，现有的理论工作仅限于小体积分数（~30%），并且大多数实验表征仅在二维（2D）上通过金相切片进行。然而，理论建模、计算模拟和三维微观结构表征方面的最新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，该项目的具体目标在于提高我们对基本材料现象的理解，发现与复杂微观结构相关的新动力学，并推进3D微观结构演变和特性的模拟和实验工具的最新技术。参与该项目的学生和初级研究人员前往大西洋彼岸的对应机构，以便沉浸在三维微观结构演化的理论、计算和实验研究中。通过学生交换项目，这些年轻的研究人员有机会发展技能，补充他们在本国机构接受的理论、模拟或实验方面的强化培训，从而获得多方面的教育经历。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.