Relaxation issues in nanoindentation experiments

This contribution reports on a systematic investigation of mechanical properties of coarse grained, polycrystalline titanium samples and antimony doped SnO2 thin films (ATO) by depth sensing indentation (nanoindentation) experiment. The combination of nanoindentation and atomic force microscopy provides a straightforward method to follow the indentation and relaxation process of the material, revealing not only the hardness and Young’s modulus of the sample, but also gaining information on the deformation process taking place during the indentation. A method was worked out based on computer evaluation of AFM images of nanoindentation impressions to resolve spatially the shape differences between the relaxed hardness indents and the ideal indenter pyramid. It provides a quantitative method to investigate the relaxation characteristic of different materials. Single grains in coarse-grained titanium and the ATO layers were investigated by this combined method, anisotropy and relaxation effects were studied. The hardness and Young’s modulus of the ATO layers have been found to be dependent on the preparation method, but the relaxation of various layers are largely uniform. Different Ti grains, however, have uniform hardness and Young’s modulus, but the relaxation effects in these samples show orientation dependence.