Nanocrystalline Metals and Thin Films: Quantized Plasticity, Internal Stress, and Grain Boundary Strength

纳米晶金属和薄膜：量子化塑性、内应力和晶界强度

• 批准号: 0907024
• 负责人: Peter Anderson
• 金额: $ 36万
• 依托单位: Ohio State University Research Foundation -DO NOT USE
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0907024&HistoricalAwards=false
• 关键词: Nanocrystalline; Metals; Thin; Films; Quantized

TECHNICAL SUMMARY:The proposed research aims to understand unusual characteristics of nanocrystalline metals through study of the underlying physics of deformation. This is accomplished by developing a new continuum description called quantized crystal plasticity and informing it with results from atomistic simulations and mechanical testing. The atomistic studies achieve this by measuring distributions of critical strength to trigger slip events. They also explore fundamental descriptions of the local features of grain boundaries that control dislocation absorption, repulsion, and nucleation. In this sense, two scales of simulation?continuum and atomistic?are coupled. The informed quantized crystal plasticity model can address experimentally relevant sample sizes and strain rates that are not possible with atomistic simulations. Specifically, the model is coupled to tensile experiments to study stress-assisted grain growth and the effect of bimodal grain size distributions on nc ductility. There are two primary expected technical outcomes of this work. The first is a fundamental description of the distribution of critical strengths and distribution of internal stress state in nanocrystalline metals. This includes an understanding of how these distributions evolve with macroscopic deformation. The second is a finite element based model that captures these features, and permits the prediction of the mechanical response of nanocrystalline metals to various stress or deformation paths. These outcomes provide a basis for structure-mechanical property relations for nanocrystalline metals.NON-TECHNICAL SUMMARY:Nanocrystalline metals embody an extreme strategy to make a high strength metal?namely to shrink the size of individual crystals to only a few hundred atoms across. This can reduce or eliminate defects that traditionally weaken metals and also introduce barriers that strengthen the metal. Indeed, nanocrystalline metals show promise in terms of extraordinary resistance to yielding, large fracture energy at low temperature, and improved resistance to failure under oscillating loads (fatigue). The proposed work will team researchers from US and international institutions to understand the fundamental strengthening processes. A key outcome is a computational tool to predict the mechanical properties of nanocrystalline metals based on their underlying structure. This enables optimization of the performance of such materials. Two graduate students will be trained in the use of advanced computational and experimental techniques. They will also assist in the development, implementation, and refinement of project-based learning modules for a new Science, Technology, Engineering, and Mathematics (STEM) secondary school. A spin off of this effort is novel, web-based interfaces to improve comprehension of materials engineering concepts, and the anticipated involvement of students from under-represented groups.

技术摘要：本研究旨在通过研究变形的基础物理原理来了解纳米晶金属的不寻常特性。这是通过开发一种称为量子化晶体塑性的新连续体描述并通过原子模拟和机械测试的结果来实现的。原子研究通过测量触发滑移事件的临界强度分布来实现这一点。他们还探索了控制位错吸收、排斥和成核的晶界局部特征的基本描述。从这个意义上说，模拟的两个尺度——连续体和原子体——是耦合的。知情的量子化晶体塑性模型可以解决原子模拟无法实现的实验相关样本大小和应变率问题。具体来说，该模型与拉伸实验相结合，以研究应力辅助晶粒生长以及双峰晶粒尺寸分布对数控延展性的影响。这项工作有两个主要的预期技术成果。第一个是纳米晶金属中临界强度分布和内应力状态分布的基本描述。这包括了解这些分布如何随着宏观变形而演变。第二个是基于有限元的模型，它捕获这些特征，并允许预测纳米晶金属对各种应力或变形路径的​​机械响应。这些结果为纳米晶金属的结构-机械性能关系提供了基础。非技术摘要：纳米晶金属体现了制造高强度金属的极端策略，即将单个晶体的尺寸缩小到只有几百个原子。这可以减少或消除传统上削弱金属的缺陷，并引入增强金属的屏障。事实上，纳米晶金属在出色的抗屈服性、低温下的大断裂能以及在振荡载荷（疲劳）下提高的抗失效能力方面表现出了良好的前景。拟议的工作将与来自美国和国际机构的研究人员合作，以了解基本的强化过程。一个关键成果是一种计算工具，可以根据纳米晶金属的底层结构来预测其机械性能。这使得此类材料的性能得以优化。两名研究生将接受先进计算和实验技术使用的培训。他们还将协助一所新的科学、技术、工程和数学 (STEM) 中学开发、实施和完善基于项目的学习模块。这项工作的一个副产品是基于网络的新颖界面，以提高对材料工程概念的理解，以及来自代表性不足群体的学生的预期参与。