Role of Defects and Stacking-Fault Energy in Deformation and Fracture of Nanotwinned Metals

缺陷和堆垛层错能在纳米孪晶金属变形和断裂中的作用

• 批准号: 1410646
• 负责人: Frederic Sansoz
• 金额: $ 28.5万
• 依托单位: University of Vermont & State Agricultural College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1410646&HistoricalAwards=false
• 关键词: Role; Defects; Stacking; Fault; Energy

Non-technical Summary:Coherent twin boundaries are defects in materials, widely described as perfect interfaces theoretically and experimentally, playing a significant role in a variety of materials. The ability of coherent twin boundaries in strengthening, maintaining the ductility, and retaining high electrical conductivity is well documented. The integration of advanced computational and experimental techniques in this research will lead to a fundamentally new understanding of plasticity and fracture in metallic metals containing these defects because of newly-developed imaging tools and computational models. The multidisciplinary research team will allow new understanding and may accelerate the deployment of the next-generation structural materials with tolerance to extreme environments such as high radiation exposure and high temperature. The education and outreach components of this project will also include research training and mentoring of undergraduate and graduate students, organization of an international symposium, and activities for attraction and retention of freshman and sophomore college students in STEM.Technical Summary:This combined computational and experimental study aims to understand the fundamental role of newly-observed kink-like twin boundary defects in the deformation and fracture of nanotwinned metals, with a particular focus on face-centered cubic metals with low and intermediate stacking-fault energies. The objectives of this project are three-fold. First, we will study new kink-dependent plastic deformation processes in model nanotwinned metals in Cu, Ag and Ag-Cu alloys using atomistic simulations tightly coupled to a new nanodiffraction mapping technique inside a transmission electron microscope, in-situ synchrotron x-ray diffraction tensile tests, and atomic force microscopy nanoindentation experiments. Second, we will examine the impact of temperature, stacking-fault energy, defect density, and grain boundary structure on hardening and softening mechanisms in these metals. Third, a multiscale approach using quasi-continuum computer simulations will be deployed to model the effects of twin boundary defects and twin size on fracture toughness. This project will benefit from the expertise of the PI in theoretical and computational materials research in nanotwinned systems, and from collaboration with scientists at Lawrence Livermore National Laboratory and Ames Laboratory who will perform state-of-the-art experiments on freestanding nanotwinned films.

共格孪晶界是材料中的缺陷，在理论和实验上被广泛描述为完美的界面，在各种材料中发挥着重要作用。共格孪晶界在强化、保持延展性和保持高导电性方面的能力是有据可查的。 在这项研究中先进的计算和实验技术的整合将导致从根本上对含有这些缺陷的金属金属的塑性和断裂有新的认识，因为新开发的成像工具和计算模型。 多学科研究团队将带来新的理解，并可能加速下一代结构材料的部署，这些材料可以耐受高辐射暴露和高温等极端环境。该项目的教育和推广部分还将包括研究培训和本科生和研究生的指导，组织国际研讨会，以及吸引和留住大一和大二学生的STEM活动。技术摘要：这项计算和实验相结合的研究旨在了解新观察到的扭结状孪晶界缺陷在纳米孪晶金属变形和断裂中的基本作用，特别关注具有低和中等堆垛层错能的面心立方金属。该项目有三个目标。首先，我们将研究新的扭结相关的塑性变形过程中的模型纳米孪晶金属在铜，银和银铜合金使用原子模拟紧密耦合到一个新的纳米衍射映射技术内的透射电子显微镜，原位同步辐射X射线衍射拉伸试验，和原子力显微镜纳米压痕实验。其次，我们将研究温度，层错能，缺陷密度和晶界结构对这些金属的硬化和软化机制的影响。第三，采用准连续介质计算机模拟的多尺度方法将部署到模型的孪晶边界缺陷和孪晶尺寸断裂韧性的影响。该项目将受益于PI在纳米孪晶系统的理论和计算材料研究方面的专业知识，以及与劳伦斯利弗莫尔国家实验室和艾姆斯实验室的科学家合作，他们将对独立的纳米孪晶薄膜进行最先进的实验。