On the Pile-Up and Sink-in Behavior of Indented Nickel Considering Dislocation Structures

Background: Surface topography of pile-up and sink-in is an issue of strain-hardening behavior around pyramidal and spherical indentations. The relationship between the surface profile and the activated dislocations is not clearly understood. Objective: This study combined electron channeling contrast imaging (ECCI), electron backscatter diffraction-based (EBSD) techniques and 3D laser microscopy to visualize the stress field and understand the influence of activated dislocations on the surface topography around an indent. Methods: The dislocation structures were identified using ECCI and geometrically necessary dislocation (GND) analysis. The stresses and GND densities were calculated to characterize the plastic deformation in terms of activated dislocations. The 3D laser microscopy was applied to reveal the surface topography. Results: The activated slip systems were identified as screw-type on (11¯1¯)[110], (11¯1¯)[101], (1¯11¯)[011], (111)[1¯10] and (111)[101¯] slip systems, and edge-type on (11¯1¯)[101], (1¯11¯)[1¯01] and (1¯1¯1)[1¯01¯] slip systems by combining ECCI and GND techniques. Furthermore, the surface morphology reveals a combination of pile-up and sink-in patterns around the indent, as observed by 3D laser microscopy. According to GND analysis, pile-up is generated from the (11¯1¯)[1¯1¯0], (111)[11¯0], (11¯1¯)[101] and (1¯1¯1)[101] slip systems, and sink-in is caused by the (1¯11¯)[01¯1¯], (11¯1¯)[1¯01¯], and (1¯11¯)[101¯]. Conclusions: The surface profile reveals a combination of pile-up and sink-in patterns resulting in the activated dislocations, where the deformation around the indent is dominated by screw-type dislocations.