Experimental characterization of micro plasticity and dislocation microstructure

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Within project P7 experimental methodologies for bending of single crystalline Ag microbeams as well as for tensile and torsion testing of Au microwires have been established. In both loading scenarios, the samples have been tested up to different degrees of plastic deformation to investigate the specific evolution of dislocation microstructure. The characterization of the deformed beams is mainly done by EBSD while the wires are examined by Laue microdiffraction using synchrotron radiation. Both methods have provided local misorientation data which in turn gave information about the dislocation structure. Thus, information about GND densities, their lateral distribution across a given cross-section, the influence of individual slip systems, as well as up to five components of the Nye tensor have been obtained. This information was analyzed in detail and processed in specific ways that it can directly be compared with Gradient Crystal Plasticity simulations of P1 (Böhlke), CDD simulations of the projects P2 (Sandfeld), P3 (Gumbsch/Schulz) and P8 (Hochrainer) as well as DDD simulations of P5 (Weygand). So far, the experimental methodologies have focused on the characterization of single crystalline samples or cross-sections. In the second funding period, the methodology will be applied to samples and microstructures with defined grain or phase boundaries in order to investigate the interaction and arrangement of dislocations at such interfaces. Therefore, we will implement micromechanical testing and characterization of epitaxially grown Au or Ag oligocrystals, coarse grained Au or Ag samples as well as single crystalline Ni base superalloys. The extension to the investigation of grain arrangements and coherent phase boundaries corresponds to the definition of the benchmark systems within the research group.