Regensburg 2007 – wissenschaftliches Programm
MM 10.4: Vortrag
Montag, 26. März 2007, 17:00–17:15, H4
Cold rolling induced amorphization and nanocrystallization processes studied by positron lifetime and 2-dimensional Doppler broadening measurements — •Wolfgang Lechner1, Werner Puff1, Herbert Rabitsch1, Gerhard Wilde2, and Roland Würschum1 — 1Institut für Materialphysik, Technische Universität Graz, Petersgasse 16, 8010 Graz, Austria — 2Institut für Materialphysik, Universität Münster
In order to contribute to an atomistic understanding of the interfacial structure and processes during amorphization and nanocrystallization, the present work deals with studies of interfacial free volumes by means of positron-annihilation-spectroscopy. In addition to positron lifetime spectroscopy, coincident Doppler broadening of the positron-electron annihilation photons is applied as novel technique for studying the chemistry of interfaces. To study the amorphization process, pure foils of Cu and Zr with a nominal composition of Cu60Zr40 were mechanically intermixed by cold rolling. Starting from the constituent pure metals, a nanoscale multilayer structure of elemental layers and amorphous interlayers develops in an intermediate state of folding and rolling, where free volumes with a Zr-rich environment occur that are presumably located in the hetero-interfaces between the various layers or in grain boundaries of the Cu-layers. To analyze the nanocrystallization reaction that occurs in marginal glass formers, pure foils of Al and Sm with a composition of Al92Sm8 were produced by the above-mentioned synthesis route. Specific modifications of free volumes and their chemical environment could be observed for various strain levels.