For very shallow indentations in W, Al, Au, and Fe-3wt%Si single crystals, hardness decreased with increasing depth irrespective of increasing or decreasing strain gradients. As such, strain gradient theory appears insufficient to explain the indentation size effect (ISE) at depths less than several hundred nanometers. Present research links the ISE to a ratio between the energy of newly created surface and plastic strain energy dissipation. Also, the contact surface to plastic volume ratio was nearly constant for a range of shallow depths. Based on the above, an analytical model of hardness versus depth provides a satisfactory fit to the experimental data and correlates well with embedded atom simulations.

Issue Section:
Technical Papers
Keywords:
indentation, hardness, plastic deformation, surface energy, iron alloys, silicon alloys, tungsten, gold, aluminium
Topics:
Aluminum, Atoms, Crystals, Deformation, Size effect, Strain gradient, Stress, Surface energy, Tungsten, Dislocations, Engineering simulation, Simulation
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