Geometrically necessary dislocation density measurements associated with different angles of indentations

• Experimental EBSD measurements of in-plane lattice rotations in a Ni single crystal.
• Lower bounds on GND densities are derived and apportioned to the active slip systems.
• Crystal plasticity FE simulations reproduces many features of the experiments.
• FE simulations indicate lower bound GND densities represent the actual state.
• Slip rate fields indicate that a kink type deformation is present in the crystal.

Experiments and numerical simulations of various angles of wedge indenters into face-centered cubic single crystal were performed under plane strain conditions. In the experiments, the included angles of indenters are chosen to be 60°,90° and 120°120° and they are indented into nickel single crystal into the 〈001¯〉 direction with its tip parallel to 〈110〉 direction, so that there are three effective in-plane slip systems on (1 1 0) plane. Indenters are applied 200μm in depth. The midsection of the specimens is exposed with a wire Electrical Discharge Machining (EDM) and the in-plane lattice rotations of the region around the indented area are calculated from the crystallographic orientation maps obtained from electron backscatter diffraction (EBSD) measurement. No matter which angles of indenters are applied, the rotation fields are very similar. There is a strong lattice rotation discontinuity on the line below the indenter tip. The magnitude of the lattice rotation ranges from -20°-20° to 20°20°. Lower bounds on the Geometrically Necessary Dislocation (GND) densities are also calculated and plotted. The numerical simulations of the same experimental setup are performed. The simulation results of lattice rotation and slip rates are plotted and compared with the experimental result. There is high correlation between the experimental result and the numerical result.