题目：Understanding the mechanical behavior of materials for MEMS and nanocrystalline mMetals
主讲人：Kevin J. Hemker
The mechanical performance of advanced structural materials is often governed by the interplay of nanoscale deformation and fracture mechanisms with underlying material’s microstructures. Modeling the reliability of MEMS and other small scale devices requires an understanding of how these mechanisms operate in micro and nanoscale structures. Microsample tensile testing and TEM have proven to be effective ways of characterizing the small-scale and scale-specific mechanical behavior of a wide variety of materials. This talk will demonstrate the utility of these techniques with case studies involving materials for MEMS and nanocrystalline metals. MEMS materials are often deposited far from microstructural equilibrium and the mechanical properties of these materials will be shown to be strongly processing, microstructure and temperature dependent. The extremely high hardness and strength of nanocrystalline materials have been well-documented, but operative deformation mechanisms in these materials have proven to be much harder to quantify.
MEMS-inspired microsample experiments will also be described and compared with TEM observations of the deformed nanocrystalline metals. Here, emphasis will be placed on the use of deformation mechanisms other than normal dislocation activity to explain the deformation characteristic of Al thin films with nanocrystalline grain sizes.
Kevin Hemker is currently a Professor in the Department of Mechanical Engineering at Johns Hopkins University, with joint appointments in the Departments of Materials Science and Engineering and Earth and Planetary Sciences. He was a NSF National Young Investigator, an invited Professor at the EPFL (1995) and the University of Paris XIII (2001), and received the ASM Materials Science Research Silver Medal in 2001. His research group is engaged in research on: the identification of processing-microstructure-property relations in materials for microelectromechanical systems (MEMS), characterization and modeling of thermal barrier coatings, deformation of nanocrystalline metals and HREM characterization of dislocation core geometries in metals and alloys. He has authored or co-authored 100 plus journal articles and conference proceedings, co-edited three books and is a principal editor of Scripta Materialia.