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DS: Dünne Schichten

DS 7: Mechanical properties of thin films

DS 7.8: Vortrag

Montag, 27. März 2006, 17:45–18:00, GER 38

Thermomechanical Properties of Thin α-Iron Films Above Room Temperature — •Thomas Wübben, Andreas Schneider, Gunther Richter, and Eduard Arzt — Max-Planck-Institut für Metallforschung, Stuttgart

The mechanical properties of thin metal films as compared to their bulk counterparts have been in the focus of materials science in the recent years. Owing to their technological importance, almost only metals with a face centered cubic structure like copper and aluminum have attracted scientific interest. Thin films made of bcc metals, on the other hand, have been largely neglected. However, from a scientific point of view, the mechanical properties of bcc metals are of special interest. As an example, the yield stress of bcc metals is strongly temperature dependent for low temperatures, while it shows a behavior similar to fcc metals for higher temperatures. The mechanisms for this so-called brittle to ductile transition (BDT) are still not understood in full detail. A major problem is the understanding of dislocation dynamics in bcc systems. As a model system we chose iron with a BDT temperature slightly above room temperature. A first step is to verify in thin films that for temperatures above the BDT the thermomechanical behavior of bcc metals resembles that of fcc metals. To test this, we applied the substrate curvature method under vacuum to thin iron films for temperatures from 40^∘C to 540^∘C. We will present results of these measurements obtained with iron films with thicknesses down to 100 nm and compare these to the thermomechanical behavior observed for metals with fcc crystal structure.