Dresden 2011 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 34: Nanomaterials I

MM 34.3: Vortrag

Donnerstag, 17. März 2011, 11:30–11:45, IFW B

Grain boundary excess volume in metals determined by dilatometry — •Eva-Maria Steyskal¹, Bernd Oberdorfer¹, Wolfgang Sprengel¹, Michael Zehetbauer², Reinhard Pippan³, and Roland Würschum¹ — ¹Inst. f. Materialphys., TU Graz, 8010 Graz, Austria — ²Phys. Nanostrukt. Mater., Fakultät f. Phys., Uni. Wien, Austria — ³Erich Schmid Institute of Mater. Sci., Leoben, Austria

The amount of excess volume in grain boundaries (GB) represents a physical key parameter which for instance determines the GB energy and GB diffusion. The direct method of time-differential dilatometry is applied in order to study the specific excess volume associated with grain boundaries by measuring the irreversible length change in submicrocrystalline (smc) Ni upon annealing-induced crystallite growth. In smc-Ni prepared by high-pressure torsion two annealing regimes occur of which the distinct stage at ca. 200^∘C is due crystal growth after structural relaxation. From the measured length decrease in this stage and the concomitant increase of the crystallite size as determined by scanning electron microscopy, an excess volume per unit area є= (0.034 ± 0.004) nm of relaxed grain boundaries is deduced. Taking into account the anisotropic grain structure, this value is independent of the measuring direction of the length change. The results will be compared with available literature data obtained from molecular dynamic simulations, high-resolution transmission electron microscopy, or indirect experimental techniques. Financial support by the FWF Austrian Science Fund is appreciated (project P21009-N20).