Nano-indentation of Cubic and Tetragonal Single Crystals

Due to the nature of their material properties, Calcium Fluoride (CaF2), Magnesium Fluoride (MgF2), and Potassium Dihydrogen Phosphate (KDP) are widely used for industrial purposes. A better understanding of the mechanical properties of these materials is of technological and scientific importance. The indentation nano-mechanical response of CaF2 (cubic), MgF2 (tetragonal), and KDP (tetragonal) optical crystals were studied and compared by using nano-indentation tests and finite element simulation with a mesoplastic formulation. Appropriate values of material parameters were determined by correlating the load-displacement curves from numerical simulations with the corresponding experimental data. The effects of elastic anisotropy and crystallographic symmetry on the load-deflection curves, surface profiles, contact radius, hardness, stress distributions, and cleavage underneath the spherical indenter at two stages, namely at maximum indentation load and after the load has been removed were also examined.