Interaction of cracks and dislocations with grain boundaries investigated by focus ion beam microscopy and nanoindentation technique

In this paper new techniques and combinations of common techniques are presented for creating well defined experiments to study the interaction of dislocations and cracks with interfaces under different loading conditions. So far, our knowledge results mostly from macroscopic tests like tensile tests or Wohler tests. However, failure mechanisms operate on the microscopic level. When experiments are done on the same scale we obtain local information of the operating mechanisms instead of average data. The presented techniques are used to proof well known models as well as to investigate the physical mechanisms in detail. One of these techniques is nanoindentation which in our case is used to measure the interaction of dislocations with grain boundaries. Another technique is electron channelling contrast imaging combined with orientation gradient mapping for a further understanding of the development of self organized ordered dislocation structures. Finally artificial crack initiation and focused ion beam tomography are used to investigate the propagation of microstructural short cracks which can not be described by common fracture mechanics.