Sharp indentation crystal plasticity finite element simulations: Assessment of crystallographic anisotropy effects on the mechanical response of thin fcc single crystalline films

Continuum crystal plasticity finite element modeling has been used to address size-effects during indentation of thin-metallic films. Berkovich indentation simulations were performed in the frame of continuum crystal plasticity to study the influence of a rigid fcc single-crystalline silicon substrate on a soft thin-metallic copper fcc single crystal film with different crystallographic orientations. It has been observed that crystallographic orientation of the indented plane has a great influence on the penetration depth at which substrate effects come into play, particularly in terms of hardness evolution. This effect has been related to the spatial arrangement of the active slip systems and the consequent plastic flow towards the substrate. In fcc crystals, indented planes that favor plastic flow along the indentation axis, such as (0 1 1) and (1 1 1) planes, are more sensitive than those in which plastic flow is favored perpendicular to the indentation axis, like (0 0 1) plane. In addition, evolution of the indentation modulus in terms of the ratio of penetrated film (penetration depth divided by film thickness) has been studied for different crystallographic orientations, showing that extrapolating the indentation modulus value from zero penetration depth reaches the same value as that found in bulk single crystals. However, indentation modulus increases linearly after the first contact, due to the elastic response of the thin films being influenced by the substrate stiffness at all penetration depths. Differences in load–displacement curves for bulk single crystals and thin, single crystalline films are justified by the elastic contrast between films and the substrate on which they are deposited.