Atomic-Scale Observation of Deformation in Nanoscale Body Center Cubic (BCC) Crystals

纳米级体心立方 (BCC) 晶体变形的原子尺度观测

• 批准号: 1536811
• 负责人: Scott Mao
• 金额: $ 34万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-10-01 至 2019-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536811&HistoricalAwards=false
• 关键词: Atomic; Scale; Observation; Deformation; Nanoscale

The metals used in mechanical components for small-scale devices at room temperature are normally of face center cubic character. Their mechanical behavior is generally well-known. However, at high temperature, these FCC metals become soft. Therefore, they are not suitable for high temperature application. In that case, body center cubic (BCC) nanostructured metals offer an alternative. These metals possess potentially desired high temperature strength. They are expected to serve in components in future high temperature device such as micro/nano electro-mechanical systems (MEMS/NMMS). Although the mechanical behavior of large-sized BCC metals is well-known, these macroscale properties cannot be directly used for nanometer-sized structures due to size effects. For the analysis of the small devices, it is necessary to know the mechanical behavior of BCC metals at small scales. However, there is lack of experimental data for the deformation process at small scales, and also there is no understanding of the deformation behavior of BCC metals at the nanometer scale. An in-situ mechanical testing approach inside a special high resolution transmission electron microscope (HRTEM) will be used in this research. This constitutes a new approach for studying the mechanical behavior at atomistic scale for nanometer-sized BCC metal specimens. The understanding of the mechanical behavior of nanometer-sized BCC crystals gained from this research will have direct impact on the design and fabrication of the high temperature MEMS/NEMS. The research on the in-situ HRTEM is expected to open a new approach to directly observe atomic-scaled deformation under mechanical stress. The results from the research are expected to contribute to the advancement of experimental mechanics and nanomaterials. The research will employ an in-situ tensile technique utilizing the most advanced instrument of high resolution transmission electron microscope (HRTEM) to reveal the deformation process in nanometer-sized BCC metal specimens. Firstly, nanometer-sized high strength BCC metal specimens will be fabricated in-situ. Secondly, tensile/compression experiment in-situ in the HRTEM will be conducted on these BCC specimens to documents deformation behavior at room temperature and high temperatures; Thirdly, lattice disturbance, dislocation dipole nucleation and competition between slip and twinning in the deformation process will be observed. Molecular dynamics modeling on key issues with a) dislocation dipole formation; b) nucleation of twinning and dislocation and c) competition of twinning and slip as function of crystal orientation will be carried out. The experiments will be carried out via national user facilities at the Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory, Richland, WA. This collaboration will build national research infrastructure.

在室温下用于小型设备的机械组件中使用的金属通常是面部中心立方特征。他们的机械行为通常是众所周知的。但是，在高温下，这些FCC金属变得柔软。因此，它们不适用于高温施用。在这种情况下，人体中心立方（BCC）纳米结构金属提供了替代方案。 这些金属具有潜在所需的高温强度。预计它们将在未来的高温设备中的组件中使用，例如微型/纳米机电系统（MEMS/NMMS）。尽管大型BCC金属的机械行为是众所周知的，但由于尺寸效应，这些宏观特性不能直接用于纳米尺寸的结构。为了分析小型设备，有必要了解BCC金属在小尺度上的机械行为。但是，在小尺度上缺乏变形过程的实验数据，而且对BCC金属在纳米尺度上的变形行为也没有理解。本研究将使用特殊高分辨率透射电子显微镜（HRTEM）内的原位机械测试方法。这构成了一种研究纳米尺寸BCC金属标本在原子量表上的机械行为的新方法。从这项研究中获得的纳米尺寸BCC晶体的机械行为的理解将直接影响高温MEM/NEM的设计和制造。预计对原位HRTEM的研究将打开一种新方法，以直接观察机械应力下的原子尺度变形。研究的结果预计将有助于实验力学和纳米材料的发展。该研究将利用高分辨率透射电子显微镜（HRTEM）的最先进的仪器采用原位拉伸技术来揭示纳米尺寸BCC金属标本中的变形过程。首先，纳米尺寸的高强度BCC金属标本将在原位制造。其次，HRTEM中的原位拉伸/压缩实验将在这些BCC标本上进行，以记录室温和高温下的变形行为；第三，将观察到变形过程中的晶格干扰，脱位偶极子核和滑移与孪生之间的竞争。分子动力学建模在a）脱位偶极子形成的关键问题上建模； b）双胞胎和脱位的成核以及c）将进行双胞胎和滑移作为晶体取向的功能的竞争。该实验将通过华盛顿州Richland的Pacific Northwest National Laboratory的环境分子科学实验室（EMSL）的国家用户设施进行。这项合作将建立国家研究基础设施。