Materials World Network: Collaborative Research: Quantifying the Role of Impurities that Control Stress-Driven Grain Growth in Nanocrystalline Metals

该材料世界网络奖支持来自宾夕法尼亚大学，约翰霍普金斯大学和悉尼大学（澳大利亚）的国际多学科研究团队，以阐明杂质对耦合晶界迁移的基本作用，如在纳米晶体金属中观察应力辅助室温晶粒生长。 这项研究的动机是最近的研究结果表明，在纳米晶金属的变形机制不仅是不同的微晶金属，但动态以及。局部晶界钉扎杂质是中央的理解，并最终控制，应力驱动的微观结构演变，但直到最近的原子级实验表征的局部掺杂剂浓度和空间分布一直是不可能的。 我们的全球团队将使用最先进的3D原子探针断层扫描技术来研究纳米晶金属薄膜中的局部结构和杂质偏析，这些薄膜是通过反应溅射合成的，以在材料中系统地引入不同数量的掺杂剂。 特别强调将放在表征的影响的内在和外在参数（晶粒尺寸，杂质含量，边界取向等）。控制晶界的杂质钉扎控制应力驱动的微观结构演变为定制纳米晶材料的机械性能提供了一条独特的途径。 微结构增强其变形机制以通过动态演化来适应应力的能力与通过局部空间控制掺杂来控制晶界迁移的阈值应力的能力的组合将促进原子级工程并可能引入一类新的材料。将开发和利用新的表征和原位测试工具和方法，推动实验纳米科学的前沿。拟议的材料世界网络团队将设计和教授针对研究和工业科学家和工程师的3D原子探针断层扫描和原位机械测试的短期课程。 本科生的拟议整合将使年轻的科学家和工程师参与新颖的国际研究活动，提供经验和机会，使学生成为更好的全球公民。

This Materials World Network award supports an international multidisciplinary research team from University of Pennsylvania, Johns Hopkins University, and University of Sydney (Australia) to elucidate the fundamental role of impurities on coupled grain boundary migration as manifest in the observation of stress-assisted room temperature grain growth in nanocrystalline metals. This study is motivated by recent findings that showed that deformation mechanisms in nanocrystalline metals are not only different to those in microcrystalline metals but are dynamic as well. Local grain boundary pinning by impurities is central to the understanding, and ultimately control, of stress-driven microstructural evolution, but until recently the atomic-level experimental characterization of local dopant concentration and spatial distribution has not been possible. Our global team will use state-of-the-art 3D atom probe tomography to investigate local structure and impurity segregation in nanocrystalline metal thin films that have been synthesized by reactive sputtering to introduce systematically varied amounts of dopants in the material. Special emphasis will be placed on characterizing the effect of intrinsic and extrinsic parameters (grain size, impurity content, boundary orientation, etc.) on both grain growth and the attendant, dynamic, mechanical behavior of nanocrystalline films.Controlling impurity pinning of grain boundaries controlling stress-driven microstructural evolution offers a unique avenue for tailoring the mechanical properties of nanocrystalline materials. The combination of a microstructure's ability to augment its deformation mechanisms to accommodate stress via dynamic evolution and control of the threshold stress for grain boundary migration by local spatially controlled doping would facilitate atomic-level engineering and potentially introduce a new class of materials. Novel characterization and in situ testing tools and methods will be developed and utilized, pushing the frontier of experimental nanoscience. The proposed Materials World Network team will design and teach short courses about 3D atom probe tomography and in situ mechanical testing targeted at research and industrial scientists and engineers. The proposed integration of undergraduate students will engage young scientists and engineers in novel and international research activities, providing experiences and opportunities that will allow students to become better global citizens.