Revisit of the anisotropic deformation behavior of single-crystal CaF2 in orthogonal cutting

A resolved stress model is presented to re-discuss the anisotropic deformation mechanism of single-crystal calcium fluoride in plunge-cut tests. The authors have investigated the machinability of CaF2 in ultra-precision cutting. However, the influence of crystal anisotropy on the brittle-ductile transition was discussed in a qualitative manner using optical microscopy and white light interferometer. Moreover, only the primary {100}<110> slip system and {111} cleavage were considered as deformation mechanisms. In this study, the ductility and brittleness of CaF2 is semi-quantitatively re-discussed on the basis of computation of the resolved stresses, by considering a secondary slip system and cleavage. The surface morphologies of the machined surface were characterized using field-emission scanning electron microscopy. The primary {100}<110> slip system is assumed to be dominant for the ductility. The brittle fracture initiated by the {111} cleavages was observed in a different manner in dependency rwith cutting directions.