Dresden 2011 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 12: Postersitzung I
MM 12.40: Poster
Montag, 14. März 2011, 17:30–19:00, P5
Structural analysis of severly deformed Ni3Ge — •Andreas Grill, Hans-Peter Karnthaler, and Christian Rentenberger — Physics of nanostructured Materials, University of Vienna, Boltzmanngasse 5, 1090 Wien
Single crystals of the L12 ordered intermetallic compound Ni3Ge were severely plastically deformed by high pressure torsion (HPT) and studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron backscattered diffraction and differential scanning calorimetry (DSC). The deformation leads to the formation of nanocrystalline bands (5 to 30 µ m wide) that are mainly occurring in regions within 100 µ m near the top and bottom surface of the HPT disc. This structural inhomogeneity is shown by SEM images and studied in detail by TEM of focussed ion beam specimens. The analysis shows three different structures occurring next to each other: (i) a highly deformed single crystalline matrix, (ii) a textured nanocrystalline structure inside of the bands and (iii) a nanocrystalline structure with little texture near the surface of the bands in a region of about 3 µ m thickness. The grain sizes in the nanocrystalline areas are about 20 nm. The average grade of disordering was investigated by DSC showing an ordering peak at 594 K; with increasing deformation the corresponding values of the enthalpies increase between 10 and 26 J/g. This result agrees with the deformation induced increase of density of bands, that show a much higher degree of disorder than the matrix as resulting from the TEM study.