Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 38: Nanostructured Materials V

MM 38.5: Vortrag

Donnerstag, 28. Februar 2008, 12:45–13:00, H 0111

Twinning during low-temperature deformation of nanocrystalline pulsed-electrodeposited nickel — •Klemens Reuther, Lutz Hollang, and Werner Skrotzki — Institut für Strukturphysik, Technische Universität Dresden, 01062 Dresden

Pure ’nanocrystalline’ nickel was produced by pulsed electro-deposition without additives for grain refinement. The average grain size of the material is d_EBSD=150 nm and d_XRD=30 nm if determined by electron backscatter diffraction (EBSD) and by X-ray diffraction (XRD), respectively. Tensile tests between 4 K and 320 K reveal that the material is ductile in the whole temperature range. Generally, the stress-strain curves are parabolic and the stress reaches its maximum after about two percent plastic strain, with the ultimate stress strongly increasing with decreasing temperature. However, there exists a critical temperature T_T=9 K below which the deformation mode suddenly changes towards twinning if the stress level reaches 2400 MPa. The twinning events are characterized by substantial stress drops accompanied by loud acoustic emissions. The microstructural changes connected with twinning will be discussed on the basis of results obtained by scanning and transmission electron microscopy.