Comparative simulation study of the structure of the plastic zone produced by nanoindentation.

Using molecular-dynamics simulation, we study nanoindentation in fcc (Cu and Al) and bcc (Fe and Ta) metals by a spherical indenter and investigate the size of the plastic zone generated. We find that while it does not strongly depend on crystal structure, surface orientation, and indentation parameters, the extent of the plastic zone is substantially larger before the retraction of the indenter. After retraction, the results are in good agreement with available published data. Plasticity develops by the generation, propagation and reaction of dislocations; they fall into two groups, those that adhere to the indentation pit, and those that have been emitted either into the substrate interior or glide along the surface. The total length of the dislocation network generated roughly follows available geometrical estimates; results for individual surface orientations may, however, differ quite strongly. The radial distribution of the dislocations attached to the indentation pit is computed; as a rule it shows a maximum at some depth below the indentation pit. [ABSTRACT FROM AUTHOR]