Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 14: Topical Session Bulk Nanostrucured Materials III - Microstructure and Characterization I

MM 14.1: Talk

Monday, March 26, 2012, 15:45–16:00, H 0107

Absolute concentration of free volumes and related properties of ultrafine grained metals studied by time-dependent dilatometry — Bernd Oberdorfer¹, •Eva-Maria Steyskal¹, Wolfgang Sprengel¹, Michael Zehetbauer², Reinhard Pippan³, and Roland Würschum¹ — ¹Inst. f. Materialphysik, TU Graz, Graz, Austria — ²Physik Nanostrukturierter Materialien, Fak. f. Physik d. Universität Wien, Wien, Austria — ³Erich Schmid Inst. of Materials Science, Leoben, Austria

Time-dependent dilatometry provides a direct approach to the absolute concentration of free volumes in nanophase materials, as it allows for a real-time observation of irreversible macroscopic length changes due to the annealing out of free volumes upon heat treatment. The ultrafine grained metals presented in this work were produced by severe plastic deformation via the high pressure torsion method. The annealing stages observed upon linear heating of severely plastically deformed iron, tantalum, copper, and nickel allow for an investigation of the absolute concentration as well as the kinetics of free volume type defects such as vacancies, dislocations, and grain boundaries [1]. Moreover a direct approach to the physical key parameter of specific grain boundary excess volume will be presented, using ultrafine grained nickel as a model system [2]. Financial support by the FWF Austrian Science Fund is appreciated (project P21009-N20).

[1] B. Oberdorfer et al., J. Alloys Comp. 509, 309 (2011)

[2] E.-M. Steyskal et al., Phys. Rev. Lett, in press