Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Topical Session Bulk Nanostrucured Materials IV - Microstructure and Characterization II
MM 20.3: Vortrag
Dienstag, 27. März 2012, 11:00–11:15, H 0107
Electron microscopic studies of Ni3Ge deformed by high pressure torsion — •Andreas Grill, Hans-Peter Karnthaler, and Christian Rentenberger — University of Vienna, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Wien, Austria
Nanocrystalline L12 ordered intermetallics processed by high pressure torsion (HPT) show improved mechanical properties [1]. The persistance of larger grains oriented for multiple slip embedded in the nanocrystalline structure indicates that highly symmetric orientations are less favourable to form nanograins [2]. To study the evolution process of nanocrystallization as a function of orientation single crystalline L12 ordered Ni3Ge of two different initial orientations was deformed by HPT. The structure of the samples was investigated by electron microscopy methods. At low numbers of turns electron backscatter diffraction of the cross section of the HPT discs shows homogeneous fragmentation. At higher numbers of turns bands are formed inhomogeneously. They cross the fragmented matrix and accumulate near the top and bottom surfaces. Transmission electron microscopy studies show that the bands consist of elongated nanograins whereas the neighbouring regions are fragmented crystallographically by a high density of defects accumulating on highly activated {111} glide planes. Finally, in the present case the different orientations seem to have little influence on the deformation structures.
[1] K. Tsuchiya, O. Ciuca. Mat. Sci. For. 667-669, 17 (2011). [2] C. Rentenberger, H. P. Karnthaler. Int. J. Mat. Res. 98, 4 (2007). This work was supported by the Austrian Science Fund (FWF): [P22440].