Regensburg 2007 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 39: Mechanical properties I
MM 39.7: Vortrag
Donnerstag, 29. März 2007, 17:45–18:00, H6
Change of deformation mechanism in sub-microcrystalline PED nickel during cyclic loading — •Lutz Hollang1, Ellen Hieckmann2, and Werner Skrotzki1 — 1Institut für Strukturphysik, Technische Universität Dresden, 01062 Dresden — 2Institut für Angewandte Physik, Technische Universität Dresden, 01062 Dresden
Sub-microcrystalline (smc) nickel produced by pulsed electrodeposition (PED) was cyclically deformed at room temperature at different plastic strain amplitudes 10−4 ≤ єpa ≤ 10−2. The standard plastic strain rate єp = 2 · 10−5 s−1 was repeatedly varied to determine the derivative (∂σa /∂lnєp)T as a function of the stress amplitude σa. Both, σa and (∂σa / ∂lnєp)T are rather high in the as-prepared state, but significantly decrease during cycling at constant єpa ≥ 2.5 · 10−4 until the specimens exhibit strain localization leading to fracture. X-ray diffraction and transmission electron microscopy reveal that the smc PED nickel cannot resist to ongoing cyclic deformation at room temperature. Already at relatively small єpa dynamic recovery and grain growth processes substantially diminish the internal stresses and transform the as-prepared smc microstructure into a recovered microcrystalline state. The (∂σa/ ∂lnєp)T vs. σa relationship indicates a gradual change of the rate-controlling process from dislocation–grain boundary interaction at the beginning of cyclic deformation to classical dislocation–dislocation interaction immediately before fracture.