Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 51: Nanomaterials - Nanocrystalline & Porous Materials I
MM 51.2: Vortrag
Donnerstag, 14. März 2013, 10:30–10:45, H25
Investigation of the grain boundarie excess free volume in nanocrystalline Pd90Au10 under plastic deformation — •Michael J. Deckarm, Jonas Heppe, Björn Lechthaler, Christian Braun, Manuel Grewer, and Rainer Birringer — Universität des Saarlandes, FR 7.2 Experimentalphysik, Campus D2.2, 66123 Saarbrücken
In as-prepared nanocrystalline (nc) materials, grain boundaries (gb) are usually in a local nonequilibrium configuration, reflecting the preparation history. A two-stage recovery process of as prepared nc Pd90Au10 has been found [1]: First a reduction of the excess free volume at lower temperatures followed by grain growth at higher temperatures. Thus by careful annealing the nanocrystalline specimen below the onset temperature of grain growth, it is possible to locally equilibrate the gb by reducing their excess free volume but avoiding grain growth. As a result, the change of the free volume in the gb can be deduced by density measurements. Moreover, using calorimetry we can determine the excess enthalpy resulting from plastic deformation of the equilibrated samples, so obtaining the relation between stored excess enthalpy and excess free volume. Combining the results from XRD, density and thickness measurements, we find that deformation is accompanied by reduction of excess free volume.
[1] A. Tschöpe, R. Birringer and H. Gleiter; Calorimetric Measurements of the Thermal Relaxation in Nanocrystalline Platinum; Journal of Applied Physics (USA). Vol. 71, no. 11, pp. 5391-5394. 1 June 1992