Berlin 2008 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 11: Nanostructured Materials III
MM 11.4: Talk
Monday, February 25, 2008, 15:30–15:45, H 0107
Influence of high pressure torsion on precipitation in Al-Cu-Mg alloys studied by positron annihilation spectroscopy. — •Wolfgang Lechner1, Werner Puff1, Michael Zehetbauer2, Erhard Schafler2, and Roland Würschum1 — 1Institut für Materialphysik, Technische Universität Graz, Petersgasse 16, 8010 Graz, Austria — 2Fakultät für Physik, Forschungsgruppe Physik Nanostrukturierter Materialien, Universität Wien, Boltzmanngasse 5, Universität Wien, 1090 Wien, Austria
High pressure torsion (HPT) may open up an efficient way to refine precipations of supersaturated solutions. In the present work, the influence of HPT on the precipitation in Al-Cu-Mg alloys and on the evolution of the precipitates with subsequent annealing is studied by positron annihilation spectroscopy. HPT is observed to give rise to a fragmentation of metastable nanoscaled precipitates which have formed upon pre-annealing at 200°C (3 hours). Positron lifetime spectroscopy in combination with coincident Doppler broadening of the positron-electron annihilation enables a specific and chemical sensitive distinction between interfacial vacancy-type defects associated with precipitates and the vacancy-type lattice defects formed upon high pressure torsion. Different aging behaviour is observed for undeformed and HPT-deformed samples. Financial support from the Austrian Science Found (FWF) under contracts P18111-N02 and P17095-N02 is gratefully acknowledged.