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In-situ, transient and high dynamic testing at the micron scale: studying time dependent plasticity and high cycle fatigue of nanocrystalline and single crystalline metals

Tuesday (27.09.2016)
16:45 - 17:00
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In-situ nanoindentation and micropillar compression are increasingly used to assess the mechanical properties and deformation behavior of thin films, individual phases and small scale structures. Off late, these techniques have been extended to high temperatures and high strain rates. This presentation will report the development of a novel piezo-based indentation technique that allows accessing extremely high strain rates (up to 10^5 per second) and high oscillation frequencies (up to 10 kHz). Validation data on standard reference materials like single crystal Si and fused silica will be presented to demonstrate the stability of the developed instrument, experimental testing protocol and test results.

Micro scale, high cycle fatigue data on nanocrystalline and single crystalline metals (both Ni) using this newly developed indentation technique will be presented. Due to high oscillation frequencies, it is now possible to access 1-10 million cycles in a reasonably short span of time. The results will be discussed and compared to existing literature. In addition, time dependent plasticity of these materials studied using creep, strain rate jump and stress relaxation tests will be presented. Based on the extracted activation parameters, the operative deformation mechanism(s) will be discussed. It is hoped that this study will pave the way for routine time dependent plasticity and fatigue tests of metals at the micron scale.

 

Speaker:
Dr. Gaurav Mohanty
Swiss Federal Laboratories for Materials Science and Technology (EMPA)
Additional Authors:
  • Dr. Jakob Schwiedrzik
    EMPA - Swiss Federal Laboratories for Materials Science & Technology
  • Serge Grop
    Alemnis Gmbh
  • Juri Wehrs
    EMPA - Swiss Federal Laboratories for Materials Science & Technology
  • Dr. Jean-Marc Breguet
    Alemnis Gmbh
  • Dr. Johann Michler
    EMPA - Swiss Federal Laboratories for Materials Science & Technology