Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 36: Nano structured materials IV

MM 36.2: Vortrag

Donnerstag, 29. März 2007, 15:00–15:15, H4

The effect of grain size on strain rate sensitivity and activation volume — •Kerstin Schüler, Delphine Lemaire, Thomas Waschkies, Bo Yang, and Horst Vehoff — Werkstoffwissenschaft und Methodik, Universität des Saarlandes, 66123 Saarbrücken, Deutschland

The strain rate sensitivity of nanocrystalline (nc) nickel (Ni) was studied at different temperatures in tensile tests and with a nanoindenter in order to examine the effect of grain size on the different deformation mechanisms of nc materials. The experiments yielded, depending on temperature and strain rate, the strain rate sensitivity, the activation volume and the creep exponents as a function of stress and grain size. From the creep experiments the transition between grain boundary sliding and dislocation climb as a function of temperature was obtained. The strain rate jump tests gave extremely small activation volumes, nearly a factor of 100 smaller than in conventional Ni as a function of grain size. For understanding this behaviour the strain rate sensitivity of single grains was tested with a nanoindenter. The results clearly showed that the primary interaction of dislocations with grain boundaries is the reason for the observed strong rate effects and small activation volumes.