Sixth GAMM Seminar on Microstructures - Abstract

Raabe, Dierk

3D studies on crystallographic texture and size effects at nanoindents and in compressed micro-pillars in Cu single crystals using 3D FIB-EBSD and crystal plasticity finite element simulations

The microstructure and texture changes underneath conical nanoindents in Cu (111) single crystals are investigated at different indentation forces. The theoretical investigation is carried out by introducing the problem in a 3D crystal plasticity based finite element simulation where two different constitutive material models are used. The theoretical findings are compared with experimental observations revealed form a 3D experiment which uses sets of subsequent (112) planes conducted in serial sectioning by a focused ion beam (FIB) system in the form of a cross-beam 3D crystal orientation microscope (3D EBSD). The used elastic-viscoplastic crystal plasticity model predicts a pronounced deformation-induced 3D patterning of the lattice rotations below the indent. This is characterized by an outer tangent zone with large absolute values of the rotations and an inner zone closer to the indenter axis with small rotations. Yet it fails to predict the fine details of the rotation patterning with the frequent changes in sign observed in the experiment and over-emphasizes the magnitude of the rotation field compared with the experiments. These differences between simulation and experiment encouraged the implementation of a physically-based crystal plasticity model for FCC materials into the crystal plasticity FEM. The model adopts the evolution of the dislocation density as a source of material hardening. In addition to the statistically stored dislocations, the geometrically stored dislocation density is introduced in order to consider the strain gradients, which are of great importance due to the geometry of the loading. Similar numerical studies are conducted on micro-pillar compression tests.
medskip Joint work with N. Zaafarani, F. Roters, S. Zaefferer, Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, 40237 Düsseldorf, Germany
medskip Wang, Raabe, Klüber, Roters, Acta Mater. 52 (2004) 2229
Zaafarani Raabe, Singh, Roters, Zaefferer, Acta Mater. 54 (2006) 1707
Ma, Roters, Raabe, Acta Mater. 54 (2006) 2169
Ma, Roters, Raabe, Acta Mater. 54 (2006) 2181