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MM: Fachverband Metall- und Materialphysik

MM 39: Mechanical properties I

MM 39.6: Vortrag

Donnerstag, 29. März 2007, 17:30–17:45, H6

Artificial crack initiation and investigation by focused ion beam microscopy — •Wolfgang Schäf, Michael Marx, and Horst Vehoff — Universität des Saarlandes, Werkstoffwissenschaft und Methodik, Postfach 151150, D 66041 Saarbrücken

The influence of the microstructure on fatigue crack growth is of interest in respect to increasing the lifetime of construction materials. A method to investigate the interaction of grain boundaries with short cracks is to introduce micro notches by Focused Ion Beam (FIB) milling in a given distance to a grain boundary. During cyclical loading, a microcrack initiates at the notch tips. The interaction between crack and grain boundary can be studied by measuring the crack velocity in respect to the distance from the grain boundary. A three dimensional tomography of the crack plane and the grain boundary can be revealed by FIB tomography with a resolution comparable to a scanning electron microscope. By this technique, it is possible to visualize the crack plane twist and tilt at a grain boundary. Further, the influence of carbide precipitates on crack growth in a nickel based superalloy was examined. It is shown that this method can also be applied to pure nickel and duplex stainless steel.