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

非技术性总结大多数固体材料，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。这项研究的目标是为金属和陶瓷中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工艺条件来实现特定的微结构和性能，从而加速将多晶部件整合到器件和结构中。该项目将依赖于对晶界生长的实验观察、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相一致。技术总结当材料在高温下加工时，晶界网络的结构由晶界迁移决定。因此，控制材料性能的前提是了解和控制晶界迁移。目前流行的两种晶界迁移模型是扩散迁移和缺陷控制迁移。为了准确地模拟微观组织的演变，有必要知道这两个模型是否以及在什么条件下提供了对晶界迁移的准确描述。X射线显微镜将被用来测量铁素体铁、镍和钛酸锶中的晶界网络结构，以及它们是如何随时间演变的。现场加热实验将被用来测量多晶体中晶界的迁移速度作为温度的函数。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，以确定哪一种理论对温度依赖性的描述更好。然后，这些力学信息将被用来对三维中尺度晶粒生长模型进行参数化。然后，这一过程的结果可以指导实验到最重要的温度范围或时间尺度上进行退火。了解界面迁移的机制将使更好地预测微结构演变成为可能，这是加速多晶材料发展的必要步骤。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.