A systematic range of nano-indentation measurements on (001) KCl single crystals was performed to differentiate between true size effects and other factors that could give rise to an apparent increase in hardness. The hardness and Young's modulus values were determined by combining the load-displacement data with measurement of the topography of the residual indent using atomic force microscopy. The latter data allowed the estimation of the true contact area, subsequently used to recalculate the hardness and Young's modulus of the material more accurately. It was shown that there was an apparent increase in hardness as the applied load decreased. The results obtained were considered in terms of different dislocation models describing the indentation size effect involving models based on both bulk and surface effects.

Dislocation Indentation Size Effect in KCl Single Crystals. Y.M.Soifer, A.Verdyan: Physica Status Solidi A, 2005, 202[13], 2454-61