Font Size: 

Increasing the resistance of materials to fatigue crack growth by optimizing the
microstructure is one major task of materials science. In this regard, grain
boundaries and precipitates are well known to decelerate short cracks, influenced
by many parameters like crack length, distance to obstacles or orientation of
adjacent grains. A comprehensive understanding of the underlying physical
principles is missing.
The focused ion beam microscope offers new possibilities for systematic
experiments and three dimensional investigations to quantify the microstructural
impact. The ion beam is used to cut micro-notches as initiation sites for cracks.
Contrary to natural cracks the influencing parameters can be varied independently
for a systematic investigation of the mechanisms.
Additionally, the ion beam is used for tomography of the crack path and the
surrounding microstructural elements. Thereby it is possible for the first time to
reveal quantitative data of the effect of microstructural barriers on short fatigue
crack growth.