Dresden 2003 – wissenschaftliches Programm
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M: Metallphysik
M 23: Mechanische Eigenschaften IV
M 23.4: Vortrag
Dienstag, 25. März 2003, 17:15–17:30, IFW B
A unified description of creep in pure and dispersion strengthened copper — •Martin Heilmaier1 and Jeffery C. Gibeling2 — 1Institut für Werkstofftechnik und Werkstoffprüfung, Otto-von-Guericke-Universität Magdeburg, D-39016 Magdeburg — 2Dept. of Chem. Engg. and Mater. Sci., University of California Davis, Davis, CA 95616
Current models have proven unsuccessful in fully rationalizing the unusual creep characteristics of dispersion strengthened (DS) metals such as a high value of the activation energy for creep and the specific quantity and temperature dependence of the particle-induced threshold stress, σp. In order to overcome these shortcomings, we propose a model that rests on the idea that internal back stresses develop during creep due to dislocation/dislocation and dislocation/dispersoid interaction. Thus, the effective stress rather than the applied creep stress is considered to be the key factor for dislocation motion. As a consequence, this approach enables a unified description of steady-state creep of copper with and without dispersoids by a single set of microstructurally-founded parameters. In addition, the temperature dependence of the creep resistance and of σp are correctly reflected. Finally, the major difference in constant structure creep after stress reductions is also predicted: while in pure copper the constant structure creep rate is lower than the eventual steady-state rate, the opposite behavior is observed in DS copper.