Collaborative Research: DMREF: Uncovering Mechanisms of Grain Boundary Migration in Polycrystals for Predictive Simulations of Grain Growth

大多数固体材料，包括金属、陶瓷，甚至一些聚合物，都有一个内部的晶界网络，将单个晶体分开。这种晶界网络强烈地影响着材料的性能，因此，对于汽车、飞机、计算机和许多其他设备的设计是重要的。本研究的目的是为金属和陶瓷的晶界网络的演变开发准确的预测模拟。这些模拟将通过定义加工条件来实现特定的微结构和性能，从而加速多晶元件与器件和结构的结合。该项目将依赖于晶粒生长的实验观测、晶界迁移的新理论和晶界网络演化的计算机模拟之间的迭代反馈。通过这种方式，它与材料基因组计划保持一致。技术总结：材料在高温下加工时，晶界网络的结构是由晶界迁移决定的。因此，控制材料性能的前提是理解和控制晶界迁移。晶界迁移的两种主要模式是扩散迁移和缺陷控制迁移。为了准确地模拟微观组织演变，有必要知道这两种模型是否以及在什么条件下能准确描述晶界迁移。x射线显微镜将用于测量铁素体铁、镍和钛酸锶的晶界网络结构，以及它们如何随时间演变。原位加热实验将用于测量多晶中晶界随温度的迁移速率。结果将与晶界迁移的原子模拟和两种晶界迁移理论的预测进行比较，以确定哪一种理论提供了对温度依赖性的更好描述。这些机制信息将用于参数化三维中尺度晶粒生长模型。然后，该过程的结果可以指导实验到最重要的退火温度范围或时间尺度。了解界面迁移机制将有助于更好地预测微观结构的演变，这是加速多晶材料发展的必要步骤。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYMost solid materials, including metals, ceramics, and even some polymers, have an internal network of grain boundaries that separate individual crystals. This grain boundary network strongly influences materials properties and, therefore, is important for the design of automobiles, aircraft, computers, and many other devices. The goal of this research is to develop accurate predictive simulations for the evolution of the grain boundary network in metals and ceramics. These simulations will accelerate the incorporation of polycrystalline components into devices and structures by defining processing conditions to achieve specific microstructures and properties. The project will rely on iterative feedback between experimental observations of grain growth, new theories for grain boundary migration, and computer simulations of the evolution of the grain boundary network. In this way, it is aligned with the Materials Genome Initiative.TECHNICAL SUMMARYThe structure of the grain boundary network is determined by grain boundary migration when the material is processed at high temperature. Therefore, controlling materials properties is predicated on understanding and controlling grain boundary migration. The two prevailing models for grain boundary migration are diffusive migration and defect-controlled migration. To accurately simulate microstructure evolution, it is necessary to know if, and under what conditions, these two models provide an accurate description of grain boundary migration. X-ray microscopy will be used to measure the structure of the grain boundary networks in ferritic iron, nickel, and strontium titanate, and how they evolve with time. In situ heating experiments will be used to measure the migration rates of grain boundaries in polycrystals as a function of temperature. The results will be compared to atomistic simulations of grain boundary migration and to predictions from two theories for grain boundary migration to determine which one provides a superior description of the temperature dependence. The mechanistic information will then be used to parameterize three-dimensional mesoscale grain growth models. The outcome of this process can then guide the experiments to the most important temperature ranges or time scales for annealing. Understanding the mechanism of interface migration will make it possible to better predict microstructure evolution, a necessary step in accelerating the development of polycrystalline materials.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.