Observation of Grain Boundary Sliding in an Ultrafine Grained Ferrite SteelWednesday (26.09.2018) 15:15 - 15:30 S1/01 - A3 Part of:
The deformation behavior and mechanisms of materials at large strains have been investigated intensively in a variety of fields such as cold forging, severe plastic deformation or tribology. During the SPD-related forming process linear flow splitting a strongly elongated pancake UFG microstructure with strong rolling texture is produced. Experimental investigations have shown that microstructural refinement saturates at a certain stage (below typical saturation levels found in high pressure torsion) even though the strain should nominally increase during further processing. To understand the deformation behavior as well as the mechanisms behind the saturation in grain size in the linear flow splitting process the local deformation behavior of the pancake microstructure under compression is of high interest. In the present work, micropillars with a polished facet were FIB milled and compressed inside an SEM using an in-situ nanoindenter with a diamond flat punch. The facet was used to observe of the microstructure of the pillar during the compression as well as to perform EBSD before and after the compression and thereby obtaining information about the grain orientation. The in-situ observation revealed that the majority of the deformation of the pancake microstructure is carried by the movement of grains relative to each other along their grain boundaries.