Nanomechanics on deformation processes in nanocrystalline materials

纳米材料变形过程的纳米力学。Mao，机械工程与材料科学系，爱丁堡大学纳米晶体（nc）材料具有超高的屈服强度，上级耐磨性和超塑性变形能力。在极低的晶粒尺寸范围内（小于20 nm），屈服强度随着晶粒尺寸的减小而降低。本项目的重点是通过关键的纳米力学实验发现极低晶粒尺寸的纳米材料的变形过程：1）原位暗场透射电子显微镜（TEM），2）原位高分辨率TEM和3）原位纳米束电子衍射。它将产生新的见解，在nc材料的独特变形过程，如GB滑动，应力诱导的晶粒团聚和晶格/GB位错动力学。因此，直接证据塑性变形过程中的数控材料将提供。期望找到与其单个晶粒行为的“最强晶粒尺寸”关系。新型原位实验的研究有望对纳米尺度实验力学和纳米材料的发展产生直接影响。此外，该项目将通过以下方式整合研究和教育：（一）为研究生和本科生提供培训，并通过研究生参与能源部国家实验室进行教育;（二）“纳米力学和纳米材料”课程开发;（三）通过匹兹堡大学目前的少数民族工程指导计划，增加代表性不足的群体参与研究。拟议的新实验技术将为匹兹堡大学和劳伦斯伯克利实验室的国家电子显微镜中心的多用户设施增加新的功能，该中心对所有美国大学开放。

Nanomechanics on deformation processes in nanocrystalline materialsPI: Scott X. Mao, Department of Mechanical Engineering and Materials Science, University of PittsburghNanocrystalline (nc) materials exhibit ultra-high yield strength, superior wear resistance and superplastic deformability. In extremely low grain size range (less than 20 nm), a reduction of yield strength with decreasing grain size has been found. This project focuses on discovery of deformation processes in nc materials with extremely low grain size through critical nanomechanical experiments: 1) in-situ dark field transmission electron microscope (TEM), 2) in-situ high resolution TEM and 3) in-situ nano beam electron diffraction. It will produce new insights regarding unique deformation process in nc materials such as GB sliding, stress induced grain agglomeration and lattice/GB dislocation dynamics. Hence, direct evidence on plastic deformation processes in nc materials will be provided. It is expected to find "strongest grain size" relationship with its individual grain behavior. The research on novel in-situ experiments is expected to result in a direct impact on nanoscale experimental mechanics and nanomaterials development. Furthermore, the project will integrate research and education by (i) providing training for graduate and undergraduate students, and education through graduate students' participation in DOE national laboratories, (ii) course development in "nanomechanics and nanomaterials" and (iii) increased participation of underrepresented groups into the research through current Minority Engineering Mentoring Program in University of Pittsburgh. The proposed novel experimental technique will add new capabilities to the multi-user facilities at the University of Pittsburgh and the National Center for Electron Microscopy in Lawrence Berkeley Laboratories, which is open to all US universities.