Regensburg 2010 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 37: Mechanical Properties II
MM 37.2: Talk
Wednesday, March 24, 2010, 15:00–15:15, H16
Creep measurements on ultra-fine grained copper after high-pressure torsion straining — •Jörn Leuthold1, M. Wegner1, S. Divinski1, K. A. Padmanabhan1, D. Setman2, M. Zehetbauer2, and G. Wilde1 — 1Institut für Materialphysik, Universität Münster, Germany — 2Fakultät für Physik, Universität Wien, Austria
Ultrafine grained materials, especially such materials that have been processed by severe plastic deformation under a high hydrostatic pressure, present unique properties such as an increase in yield strength and simultaneously a considerable uniform tensile elongation before failure. The small grain size and the presence of defects with high specific excess energy densities lead to modifications of the basic mechanisms that can accommodate externally applied mechanical stresses. Grain boundary controlled mechanisms, such as grain boundary emitted dislocations and partial dislocations, twinning, grain boundary diffusion and sliding can be more important or even dominant. To study the deformation behavior, several copper samples were prepared by High Pressure Torsion, a technique to induce high shear stresses on a specimen to produce fine grained, bulk material. The characterization of the microstructure in terms of grain size distributions, misorientation of grain boundaries and texture was done by electron backscatter diffraction. A miniaturized device for creep measurements was constructed to perform tensile creep tests under uniaxial conditions at temperatures from 273K to 348K. The measurement of the activation energy for the rate controlling creep mechanism is set into context with grain boundary diffusion experiments.