Topic: Grain boundary structure and grain boundary diffusion of severely strained metals
Speaker: Univ.-Prof. Dr. Gerhard Wilde
Director, Institute of Materials Physics, University of Münster, Germany
Time: 10:00am-11:30am (Mon.), 29 October, 2012
Venue: Room 468, Lee Hsun Building, IMR CAS
Abstract:
Bulk nanostructured - or ultrafine-grained materials are often fabricated by severe plastic deformation (SPD) to break down the grain size by dislocation accumulation. Underlying the often observed property enhancement is a modification of the volume fraction of the grain boundaries. However, early concepts as well as recent results indicate that in addition to the increased volume fraction of grain boundaries in ultrafine grained materials, also the nature of at least a fraction of the grain boundaries is modified. Combined studies by radiotracer diffusion analyses and by high resolution transmission electron microscopy and geometric phase analysis indicate that these modifications can be far more complex as indicated in the picture of so-called “non-equilibrium” grain boundaries. These results also indicate that the modifications to the nature and characteristics of these grain boundaries can enhance or deteriorate the performance of the deformed materials and the comparison of differently deformed materials indicates further that the improvements or deteriorations are inherently coupled to the details of the deformation pathway.
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