Dresden 2006 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
MM: Metall- und Materialphysik
MM 12: Symposium Severe Plastic Deformation III
MM 12.1: Fachvortrag
Dienstag, 28. März 2006, 10:15–10:45, IFW A
Scaling Effects on the Plasticity of ECAP Nickel — •Lutz Hollang1, Ellen Hieckmann2, Dieter Brunner3, Carl Holste1, and Werner Skrotzki1 — 1Institut für Strukturphysik, Technische Universität Dresden, 01062 Dresden, Germany — 2Institut für Angewandte Physik, Technische Universität Dresden, 01062 Dresden, Germany — 3Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart, Germany
The influence of grain size on the interaction mechanisms between dislocations governing the plastic behaviour of fcc metals at low temperatures was studied by means of thermal activation analysis. For this purpose the plastic behaviour of sub-microcrystalline (smc) nickel processed by equal-channel angular pressing (ECAP) was investigated in tension at constant temperatures between 4 K and 320 K. Stress-relaxation experiments performed during the tensile tests were used to determine the rate sensitivity of the material as a function of the flow stress. In all cases the relationship is found to be linear revealing that the mean dislocation spacing influences both, the athermal and thermal contribution to the flow stress in the same manner as predicted by the Cottrell-Stokes law. The effect of grain size on the flow stress can be attributed to a constant additive athermal stress contribution. Moreover, the thermal activation analysis indicates that at temperatures below 100 K a local single slip mechanism governs the plastic behaviour of smc ECAP nickel. At higher temperatures other thermally activated slip processes become rate controlling. They are probably connected with the thermally activated dissolution of the initial ECAP structure.