Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 34: Topical Session Bulk Nanostrucured Materials VII - Mechanical Properties II
MM 34.3: Vortrag
Mittwoch, 28. März 2012, 12:15–12:30, H 0107
Creep measurements in HPT-processed copper having ultrafine grain size — •Jörn Leuthold1, Matthias Wegner1, Anantha Padmanabhan2, Sergiy Divinski1, and Gerhard Wilde1 — 1Institute of Materials Physics, University of Muenster, Germany — 2School of Engineering Sciences & Technology, University of Hyderabad, India
In materials processed by severe plastic deformation, the presence of a high defect density in the form of dislocations, twins, high and low angle grain boundaries (GB) and their distribution affects the plastic deformation when a shear stress is applied. With a decrease in grain size into the sub-micrometer range, a dislocation-based deformation mechanism becomes increasingly unfavorable. Therefore GB diffusion and sliding account for the rate controlling deformation process even at low homologous temperatures, i.e. the creep resistance is significantly reduced. Regardless of the rate controlling physical mechanism, the "power law" is used to describe steady state, uniaxial deformation in the high stress, low homologous temperature regime. For this study copper samples were prepared by high pressure torsion and cut into a dog bone shape to perform isothermal tensile creep experiments. From load jump experiments, the stress exponent, activation energies for rate controlling flow and the strain rate values at different stresses and temperatures are obtained. Microstructural characterization in terms of nanoindentation, electron backscatter diffraction of as prepared and creep deformed specimens, changes in hardness, grain size distribution and texture are related to the observed activation energy.