Stress-driven grain boundary movement during nanoindentation in tungsten at room temperature

What is it about?

Nanoindentations were performed in the vicinity of grain boundaries (GBs) in polycrystalline tungsten at room temperature, observing in some cases a secondary pop-in (known as GB pop-in) in the load–displacement curve. The dislocation microstructure in the plastic zone of the residual impression was analysed using sequential polishing, electron channelling contrast imaging (ECCI) and electron backscatter diffraction (EBSD) analysis on and below the surface. For some indentations, the interaction of the dislocations within the plastic zone and the GB leads to a localized GB movement on or below the surface. The occurrence and magnitude of GB movement are found to be strongly influenced by misorientation between the adjacent grains, the orientation of the indenter, as well as the applied load and the distance to the GB. The results show that the localized GB movement under an inhomogeneous stress field at room temperature is a possible deformation mechanism for tungsten.

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