Collaborative Research: EAGER: Interactions Between Dislocations and Grain Boundaries in BCC Metals: Hall-Petch Effect

技术摘要：将构建一个包含大量离散位错效应的数值易处理的多尺度模型，并与基于电子背散射衍射（EBSD）的表征进行比较，以解决长期存在的开放性问题：？为什么多晶金属的机械强度会随晶粒尺寸而变化（霍尔-佩奇效应）？该模型将避免任意的长度尺度（应变梯度）和未观察到的微观结构（线性堆积）。相反，将构建和测试预测能力。新的建模和表征能力将使材料设计和改进应用成为可能，例如金属成形，特别是钢等体心立方金属。这些进展将被纳入两所参与大学的教学模块;本科生和研究生将接受研究实践培训; EBSD灵敏度将扩展到两个数量级;结果将通过同行评议的出版物、论文和学位论文广泛传播。非技术摘要：常见结构金属（如钢、铜、铝、钛）的强度随其微观结构的尺度而变化很大。例如，仅通过改变晶粒尺寸就可以使钢的强度提高10倍。 目前还没有确定的机制或模型可以定量预测这种众所周知的效应。为了便于设计和使用更好、更强的材料，将使用新的分析技术构建和测试一个预测性多尺度（微观/宏观）模型。从根本上理解这一重要效应的好处将允许生产和使用更好的材料，从而产生各种社会优势，例如增加个人和国家安全，减少燃料消耗和减少温室气体排放。

Technical Summary:A numerically tractable multi-scale model incorporating the effects of large numbers of discrete dislocations will be constructed and compared with novel electron-backscattering diffraction (EBSD)-based characterization to address the long-standing open question: ?Why does the mechanical strength of polycrystalline metals vary with grain size (Hall-Petch Effect)?? The model will avoid arbitrary length scales (strain gradients) and unobserved microstructures (linear pile-ups). Instead, a predictive capability will be constructed and tested. The new modeling and characterization capabilities will enable material design and improve applications, e.g. metal forming, particular for body-centered cubic metals such as steels. The advances will be incorporated in instructional modules at the two participating universities; undergraduate and graduate students will be trained in research practices; EBSD sensitivity will be extended by up to two orders of magnitude; and results will be disseminated widely by peer-reviewed publications, theses, and dissertations.Non-Technical Summary:The strength of common structural metals (e.g. steel, copper, aluminum, titanium) varies greatly with the scale of its microstructures. For example, the strength of steel can be increased 10 times by changing the grain size alone. There is no confirmed mechanism or model that predicts this well-known effect quantitatively. In order to facilitate the design and use of better, stronger materials, a predictive multi-scale (micro/macro) model will be constructed and tested using new analytical techniques. Benefits of a fundamental understanding of this important effect will permit production and use of better materials, resulting in a variety of societal advantages such as increased personal and national safety, reduced fuel consumption, and reduction of greenhouse gas emissions.