title: Grain boundary excess volume and defect annealing of copper after high-pressure torsion.
abstract: The release of excess volume upon recrystallization of ultrafine-grained Cu deformed by high-pressure torsion (HPT) was studied by means of the direct technique of high-precision difference dilatometry in combination with differential scanning calorimetry (DSC) and scanning electron microscopy. From the length change associated with the removal of grain boundaries in the wake of crystallite growth, a structural key quantity of grain boundaries, the grain boundary excess volume or expansion [Formula: see text] m was directly determined. The value is quite similar to that measured by dilatometry for grain boundaries in HPT-deformed Ni. Activation energies for crystallite growth of [Formula: see text] and [Formula: see text] are derived by Kissinger analysis from dilatometry and DSC data, respectively. In contrast to Ni, substantial length change proceeds in Cu at elevated temperatures beyond the regime of dominant crystallite growth. In the light of recent findings from tracer diffusion and permeation experiments, this is associated with the shrinkage of nanovoids at high temperatures.
authors.affiliation: Institute of Materials Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: Bernd
authors.initials: B
authors.lastname: Oberdorfer
authors.affiliation: Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, A-1090 Vienna, Austria.
authors.forename: Daria
authors.initials: D
authors.lastname: Setman
authors.affiliation: Institute of Materials Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Steyskal
authors.affiliation: Erich Schmid Institute of Materials Science, University of Leoben, A-8700 Leoben, Austria.
authors.forename: Anton
authors.initials: A
authors.lastname: Hohenwarter
authors.affiliation: Institute of Materials Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sprengel
authors.affiliation: Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, A-1090 Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Zehetbauer
authors.affiliation: Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, A-8700 Leoben, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Pippan
authors.affiliation: Institute of Materials Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Würschum
keywords: Dilatometry; Grain boundaries; Grain growth
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