Probing the Evolution of Granular Microstructures during Dynamic Annealing via Integrated Three-Dimensional Experiments and Simulations

通过集成三维实验和模拟探讨动态退火过程中颗粒微观结构的演变

• 批准号: 2104786
• 负责人: Katsuyo Thornton
• 金额: $ 57.24万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2104786&HistoricalAwards=false
• 关键词: Probing; Evolution; Granular; Microstructures; during

Non-technical SummaryMany metallic materials are polycrystalline, in which a solid consists of many tiny crystals (“grains”) with different orientations. In some cases, superior properties can be achieved when the material is made in a single-crystal form, as in the case for jet-engine turbine blades, shape-memory alloys, and solar cells. However, single crystals are expensive and time-consuming to produce. Recently researchers have found that single crystals can be produced through abnormal grain growth induced by cyclic heat treatment, where the metal alloy is heated and cooled repeatedly. During abnormal grain growth, a few grains preferentially grow by engulfing the neighboring grains. The goal of this project is to discover why and how this process occurs. The project integrates emergent research in experimental characterization and simulations of the grain growth process, capitalizing on the ability to watch the evolution of the polycrystalline microstructure in real-time and leveraging high-performance computing to simulate microstructural evolution. Developing the fundamental understanding of abnormal grain growth could lead to a paradigm shift in the manufacture of single-crystalline materials, and therefore it promotes global competitiveness in manufacturing and technology and national prosperity. The project also promotes the development of a highly trained future workforce; two graduate students are trained in state-of-the-art techniques in experiments, modeling, simulations, and data analysis. Outreach activities are carried out through the Females Excelling More in the Math, Engineering, and the Sciences program and Washtenaw Elementary Science Olympiad and include a virtual reality demonstration that allows students to walk through an evolving microstructure during heat treatment. Technical SummaryA cyclic heat treatment, in which precipitates are repeatedly formed and dissolved by thermal cycling, holds promise for solid-state processing of single crystals and otherwise large-grained materials via abnormal grain growth. However, its full potential has not been realized due to the poor understanding of the mechanisms underlying the process. The objective of this project is to advance the science governing the growth of the abnormal grains during non-isothermal annealing. The following fundamental questions are addressed: What is the mechanism by which abnormal grain growth is initiated under dynamic thermal environment? Which grains are most likely to become abnormal and what are their microstructural signatures? How does the abnormal grain grow into new microstructural neighborhoods? To answer these questions, emergent research in structural characterization, phase-field and phase-field-crystal modeling, and graph theory methods are synergistically integrated. High-resolution synchrotron-based X-ray diffraction microscopy is utilized to visualize and quantify the evolution of the grain and subgrain network in real-time and also enable microstructural evolution simulations based on the measured space-, time-, and orientation-resolved datasets as initial conditions. The resulting high-dimensional data is then distilled into a network model that succinctly describes the granular and the local driving forces for grain boundary motion, which significantly reduces the computational cost of predicting the microstructural evolution. Scientific understanding of abnormal grain growth upon thermal cycling ultimately informs the process design of single-crystal fabrication.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术总结金属材料是多晶的，其中固体由许多具有不同方向的微小晶体（“谷物”）组成。在某些情况下，当材料以单晶形式制成时，可以实现出色的特性，例如喷气引擎涡轮叶片，形状 - 内存合金和太阳能电池。但是，单晶很昂贵且耗时。最近，研究人员发现，可以通过循环热处理诱导的异常谷物生长产生单晶，在那里金属合金被反复加热并冷却。在异常的谷物生长过程中，通过吞没相邻的谷物优先生长一些谷物。该项目的目的是发现该过程的发生原因和方式。该项目将紧急研究整合在实验表征和谷物生长过程的模拟中，利用了观察多晶微观结构的演变的能力，并利用高性能计算以模拟微观结构的演变。发展对异常谷物生长的基本理解可能会导致单晶材料制造的范式转移，因此它促进了制造业和技术和国家繁荣方面的全球竞争力。该项目还促进了训练有素的未来劳动力的发展；两名研究生接受了实验，建模，模拟和数据分析的最先进技术培训。外展活动是通过女性在数学，工程学和科学课程和Washtenaw基础科学奥林匹克方面表现出色的女性进行的，其中包括一个虚拟现实演示，使学生可以在热处理期间经历不断发展的微观结构。技术摘要循环热处理，在热循环中反复形成并溶解沉淀，有望通过异常的谷物生长通过异常的固态加工单晶和其他大颗粒的材料。但是，由于对过程基础机制的理解不足，其全部潜力尚未实现。该项目的目的是推进非静脉退火期间异常晶粒生长的科学。解决了以下基本问题：在动态热环境下启动异常谷物生长的机制是什么？哪些谷物最有可能变得异常，它们的微结构特征是什么？异常的谷物生长如何进入新的微观结构社区？为了回答这些问题，在结构表征，相位场和相位晶体建模以及图理论方法方面进行了紧急研究。基于高分辨率同步加速器的X射线衍射显微镜用于实时可视化和量化谷物和亚晶粒网络的演化，还可以基于测得的空间，时间和方向分辨数据集作为初始条件，从而实现微结构演化模拟。然后将所得的高维数据提炼成网络模型，该网络模型简要地描述了晶粒边界运动的颗粒状和局部驱动力，从而大大降低了预测微结构演化的计算成本。热循环时对异常谷物生长的科学理解最终为单晶制造的过程设计提供了依据。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，通过评估被认为是珍贵的支持。