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MM: Metall- und Materialphysik

MM 23: Mechanical Properties I

MM 23.5: Vortrag

Mittwoch, 29. März 2006, 15:00–15:15, IFW B

Initiation of microcracks with predefined slip planes and directions to investigate the interaction with micro-structural barriers — •Michael Marx, Wolfgang Schäf, and Horst Vehoff — Universität des Saarlandes, Werkstoffwissenschaft und Methodik, Geb. D23, 66041 Saarbrücken

It is well known that the propagation of microstructurally short cracks can be reduced as result of the interaction with microstructure elements like grain- and phase boundaries. This effect is exploited in materials like composites and multiphase materials with defined phase and boundary conditions to get an improved toughness and fatigue resistance. Further improvement can be expected from grain boundary engineering. Therefore it is necessary to investigate the interaction mechanisms between cracks and boundaries systematically on a microscopic scale. To do this a reproducible method to initiate artificial microcracks with predicted conditions like crack length and distance from the crack tip to the boundary is needed. It will be shown that with a Focused Ion Beam (FIB) such artificial microcracks can not only be initiated but even the direction of the propagation can be predefined. This is possible due to a combination of a complete crystallographic specimen characterization by electron back scatter diffraction (EBSD) and the locally precise adjustable ion beam. So cracks can be initiated directly on the preferred slip system. As a first result the interaction of microcracks with different grain boundaries in a directionally solidified nickel based superalloy will be presented.