Nanosegregation, Microtexture and the Control of Brittle Failure

纳米偏析、微观织构和脆性破坏的控制

• 批准号: 0304738
• 负责人: David Williams
• 金额: $ 61万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0304738&HistoricalAwards=false
• 关键词: Nanosegregation; Microtexture; Control; Brittle; Failure

This grant uses a novel combination of experimental techniques to determine the interplay between local microtexture and nanometer-scale segregation of impurities to grain boundaries, which may cause brittle failure. This inter-relationship has not been examined to date, but X-ray mapping in the analytical electron microscope offers both the high spatial resolution and atomic-level detection necessary for quantitative analysis of multiple, undisturbed boundaries (i.e. not fractured prior to study) in the same specimen. Automated crystallography for the transmission electron microscope can determine the misorientation across the same boundaries. The hypothesis is that local texture can control the amount and degree of segregation or, conversely, that segregation can control the local microtexture. The understanding obtained via these new techniques would permit development of new thermo mechanical treatments to mitigate the deleterious effects of segregants and this is a primary aim of the research. The change in segregant distribution will be measured in specific textures produced either via thin film formation on tailored substrates or via grain boundary engineering which creates a high fraction of low energy boundaries to which segregation is minimized. Ideal segregating systems in Cu and Fe will be studied.%%%A broader impact of the research is that, if successful, it may offer an alternative method of the current (and expensive) practice of reducing undesirable trace elements to levels where segregation does not cause embrittlement. If segregation can be minimized by grain boundary engineering, then the very thermo-mechanical treatments used to develop desirable properties may be modified to suppress segregation simultaneously, to levels where the connectivity of brittle boundaries is lowered sufficiently to prevent crack propagation leading to brittle failure. The techniques developed will be incorporated into classroom teaching material, a 2nd edition of a major textbook and Lehigh's annual microscopy courses for industrial and government researchers.***

这项资助使用了一种新的实验技术组合，以确定局部微观结构和纳米级偏析的杂质晶界，这可能会导致脆性破坏之间的相互作用。这种相互关系还没有被检查的日期，但在分析电子显微镜中的X射线映射提供了高空间分辨率和原子级检测所需的多个，未受干扰的边界（即研究前不破裂）在同一个标本的定量分析。透射电子显微镜的自动晶体学可以确定相同边界上的取向差。假设是局部纹理可以控制偏析的数量和程度，或者相反，偏析可以控制局部显微纹理。通过这些新技术获得的理解将允许开发新的热机械处理，以减轻偏析的有害影响，这是研究的主要目的。偏析物分布的变化将在特定纹理中测量，所述特定纹理通过在定制基底上形成薄膜或通过晶界工程产生，所述晶界工程产生高比例的低能量边界，使偏析最小化。将研究铜和铁的理想偏析系统。%这项研究的一个更广泛的影响是，如果成功的话，它可能提供一种替代目前（和昂贵的）做法的方法，将不需要的微量元素减少到偏析不会导致脆化的水平。如果偏析可以通过晶界工程最小化，则可以修改用于开发所需性能的热机械处理以同时抑制偏析，达到脆性边界的连接性充分降低以防止导致脆性失效的裂纹扩展的水平。开发的技术将被纳入课堂教学材料，第二版的主要教科书和利哈伊的年度显微镜课程的工业和政府研究人员。