Nanomechanics on deformation processes in nanocrystalline materials

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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.