Inception of plasticity in the presence of vacancies in FCC single crystals: indenter size effect

摘要

Atomistic simulations of nanoindentation tests were used to study the indenter radius size effect in the presence of vacancies in a (111) single crystal of nickel. For radii from 2 nm to 8 nm, the maximum shear stresses under the indenter at the onset of plastic deformation in crystals with vacancies were compared to those which cause yield in perfect crystals by placing a single vacancy in a position near the maximum shear stress underneath the indenter tip. The effect of the presence of vacancies is lowered by decreasing the indenter radius. Results obtained for several random distributions of vacancies, in the range 3.3e-4 to 0.0033, show that placing a single vacancy near a specific location produces similar results as using larger numbers of vacancies while simplifying the complexity of the simulation. Finally, visualizations of atomic configurations of a single crystal with vacancy concentration of 3.3e-4 for radii of 4 nm and 6nm show that the heterogeneous nucleation is a size dependent phenomenon.