In-situ EBSD measurements during micro-cantilever fracture experiments in single-crystalline B2-NiAl and tungstenWednesday (28.09.2016) 14:45 - 15:00 Part of:
In order to understand the elastic-plastic fracture process at the microscale, we perform micro-cantilever experiments inside a scanning electron microscope. This allows us to investigate the deformation and fracture behavior in-situ and to correlate those observations precisely with the experimental data [1, 2]. The materials we focus on, single-crystalline B2-NiAl and tungsten, have brittle to ductile transition temperatures which are well above room temperature. This allows the study of fracture processes which are accompanied by limited plastic deformation around the crack tip. The cantilevers are prepared by focused ion beam machining and have approximate dimensions of 25 µm in length and 7 µm in thickness and width. In addition to each micromechanical test, in-situ high resolution electron backscatter diffraction measurements of the area around the crack tip are performed at various loading states by means of the cross correlation technique. In that way the evolution of local stresses and strains acting at the crack tip and leading to crack growth in the samples is accessible. By analyzing the rotation gradients in the sample, the plastic deformation in terms of geometrically necessary dislocations can be mapped, quantified and used to describe the effect of dislocations in the investigated materials on the fracture behavior.
 F. Iqbal, J. Ast, M. Göken, K. Durst, Acta Materialia Vol. 60, (2012).
 J.Ast, T.Przybilla, V. Maier, K. Durst, M. Göken, Journal of Materials Research Vol. 29 (18), (2014).