Dresden 2014 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 50: Mechanical properties III - Evolution & deformation of microstructure

MM 50.2: Talk

Thursday, April 3, 2014, 10:30–10:45, IFW B

Viscoplastic properties of copper with ultrafine grain structure after high-pressure torsion — •Jörn Leuthold, Matthias Wegner, Martin Peterlechner, Sergiy V. Divinski, and Gerhard Wilde — Institute of Materials Physics, University of Muenster, 48149 Muenster, Germany

Metals processed by severe plastic deformation possess a high density of stored energy in the form of vacancies, dislocations, twins, high- and low-angle grain boundaries. As a consequence of the grain refinement towards the sub-micrometer range, the structure and thermal evolution of grain boundaries as well as the interactions of the internal interfaces with defects in the grain interior become decisive factors for thermal stability, kinetic and plastic properties of the material. Even at low homologous temperatures, the viscoplastic flow can significantly contribute to the deformation mode when a mechanical stress is applied. In this study, 99.99% pure copper was processed by High Pressure Torsion (HPT) and investigated via nanoindentation. In addition to the determination of hardness maps, the viscoplastic properties were analyzed using long dwell times. Furthermore, uniaxial tensile tests were performed to determine the strain rate sensitivity in load jump tests. In combination with electron back scatter diffraction, the grain size and misorientation distribution and texture were analyzed in the as-deformed state and after additional tensile elongation at temperatures in the range from 293 K to 423 K. The results are discussed with respect to dislocation-mediated and grain boundary dominated mechanisms of plasticity.