Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 12: Symposium Severe Plastic Deformation III

MM 12.4: Fachvortrag

Dienstag, 28. März 2006, 12:15–12:45, IFW A

Cylic Deformation Behaviour and Fatigue Life of Ultrafine-Grained Aluminum — •Dorothea Amberger, Johannes May, Heinz-Werner Höppel, and Mathias Göken — Lehrstuhl Allgemeine Werkstoffeigenschaften, Martensstrasse 5, 91058 Erlangen

Bulk ultrafine-grained (UFG) metals with grain sizes in the sub-micrometer range can be produced by Equal Channel Angular Pressing. Generally UFG materials exhibit extraordinary mechanical properties [1,2], and show also an enhanced strain rate sensitivity (SRS). The mechanisms responsible for the SRS, like Coble creep, grain boundary sliding or thermally activated annihilation of dislocations [1,2,3,4], are still unclear. This work focuses on the influence of the strain rate of UFG Al under cyclic loading. The obtained stress amplitudes for the tests performed at a smaller strain rate are only smaller within the first hundred cycles. This is in accordance to the observations under monotonic loading. After the first hundred cycles no significant differences between the obtained stress amplitudes with respect to the strain rate were found. Based on these results it can be concluded that grain boundary sliding or coble creep cannot be the relevant mechanisms for SRS, as there is no reasonable explanation for the diminishing of the difference in the stress amplitudes during cycling. In contrast, annihilation of dislocations can quite reasonably explain these results.

[1] RZ Valiev, IV Alexandrov; J Mater Res 2002 17 (1) 5 [2] HW Höppel, J May, M Göken; Adv Eng Mater 2004 6 781 [3] YJ Li, XH Zeng, W Blum; Acta Mater 2004 52 5009 [4] J May, HW Höppel, M Göken; Scripta Mater 2005 53 189