Dresden 2009 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 37: Topical Session High Temperature Materials IV
MM 37.3: Talk
Thursday, March 26, 2009, 11:00–11:15, IFW A
In-situ investigation of crack propagation in γ-TiAl alloys using atomic force, focus ion beam and scanning electron microscopy — •Farasat Iqbal1, Florian Pyczak2, and Mathias Göken1 — 1Lehrstuhl Allgemeine Werkstoffeigenschaften, Friedrich-Alexander-Universität Erlangen-Nürnberg — 2GKSS Research Centre Geesthacht, Geesthacht
The present study is focused on crack propagation mechanism in Ti-45Al-1Cr & Ti-45Al-5Nb alloys with lamellar microstructure. Atomic force microscopy (AFM) is a versatile technique to study the crack propagation in-situ. AFM was employed to investigate the local deformations near the crack tip. Scanning electron microscopy (SEM) supplements the in-situ observations and was used to get a basic understanding of the crack propagation path over larger distances.A focused ion beam (FIB) was used to investigate the structures and deformation traces underneath the surface.
It is concluded that the γ/α2 interfaces act as favorable sites for new interfacial crack nucleation and also for interlamellar crack propagation. Nucleation of new cracks was often preceded by the interaction of deformation twins with interfaces and also by strong shear band activity in the γ-TiAl lamellae visible as significant surface topography in AFM.Mostly the underneath crack path follows the γ/α2 interface similar to the situation observed at the surface. The local misorientation measured with Electron Backscattered Diffraction (EBSD) shows γ-lamellae as the region of high deformation as compare to neighboring α2 -lamellae around the crack tip and its surroundings.