DMREF: Grain Growth Beyond Isotropic Models: Microstructure Evolution with Experimentally-Derived Interface Properties

非技术描述：几乎所有人造固体都是由许多称为颗粒的小晶体组成的。这些颗粒的大小和它们附着的方式--材料制造时决定的特性--影响着固体的许多性质。现有的加工过程中颗粒演变的模型无法预测观察到的结果。由于问题的复杂性，甚至不可能对谷物在加工过程中如何演变做出准确的预测。这项研究将检验这样一个假设，即如果包括关于颗粒之间界面性质的信息，就有可能预测材料中颗粒的演化。这项研究将把模拟与新开发的实验技术结合起来，以检验这一假说。将采用各种方法来确定当前模型的不足之处、如何改进它们，以及预测颗粒演化的可能性程度。这项研究的更广泛影响是，预测加工过程中颗粒变化的能力将使其能够避免反复试验，并以更快和更低的成本开发改进的材料。技术描述：准确预测热退火过程中微观结构的演变是材料科学中长期存在的问题之一。虽然已知平均晶粒度随退火而变化的情况，但对晶界特征分布、织构和晶形的演变却知之甚少。这项研究的主要结论是，有了晶界性质的知识，以及这些性质如何随着晶界的结晶学而变化，就有可能预测在晶界生长过程中微观结构将如何变化。将采用观察、模拟、比较和修正的连续反馈周期，目的是创建准确的、预测的颗粒生长模型。这项研究将集中在具有一系列各向异性晶界属性的材料上。铁素体铁具有最各向同性的性质。钛酸锶的晶界性质随晶界面取向变化较大。镍的晶界性质在晶格取向偏差和晶界面取向两方面都是各向异性的。本研究中对三维组织演化的研究将使检验所提出的各向异性晶界特征分布和生长停滞的发展机制成为可能。

NON-TECHNICAL DESCRIPTION: Nearly all man-made solids are made up of many small crystals referred to as grains. The sizes of these grains and the way that they are attached - characteristics determined when the material is made - influence many of the solid's properties. Existing models for the evolution of the grains during processing fail to predict observed outcomes. Because of the complexity of the problem, it is not even obvious that it is possible to make accurate predictions of how grains evolve during processing. The research will test the hypothesis that it is possible to predict the evolution of the grains within a material if information about the properties of the interfaces between the grains is included. The research will couple simulations with newly developed experimental techniques to test the hypothesis. Methods will be employed to identify where current models are insufficient, how they can be improved, and the degree to which it will be possible to predict grain evolution. The broader impact of this research is that the ability to predict how grains change during processing will make it possible to avoid trial and error experimentation and develop improved materials more quickly and at a lower cost.TECHNICAL DESCRIPTION: Predicting exactly how microstructures evolve during thermal annealing is one of the longstanding problems in materials science. While it is known how the average grain size will change with annealing, very little is known about the evolution of the grain boundary character distribution, the texture, and the grain shape. The main assertion of this research is that with knowledge of the grain boundary properties and how the properties vary with the crystallography of the grain boundary, it will be possible to predict how the microstructure will change during grain growth. A continuous feedback cycle of observations, simulation, comparison, and correction will be employed with the objective of creating accurate, predictive models for grain growth. The research will focus on materials with a range of anisotropic grain boundary properties. Ferritic iron has the most isotropic properties. The grain boundary properties of strontium titanate vary mostly with respect to grain boundary plane orientation. The grain boundary properties of nickel are anisotropic with respect to both lattice misorientation and grain boundary plane orientation. The studies of three-dimensional microstructure evolution in this research will make it possible to test proposed mechanisms for the development of anisotropic grain boundary character distributions and grain growth stagnation.