Research of material removal and deformation mechanism for single crystal GGG (Gd3Ga5O12) based on varied-depth nanoscratch testing

The varied-depth nanoscratch test is carried out on the (111) plane of single crystal GGG along < 110 > direction. Two indenters with different tip radii are used in this work. During the nanoscratch process, continuous chips and the bottom of the groove with micro cracks and slip lines are obtained by using a sharp indenter. Segmental chips and the bottom of the smooth groove are obtained by using a blunt indenter. Compared with using a blunt indenter, using a sharp indenter can obtain deeper scratch depth, deeper residual depth and lower elastic recovery under the identical normal force. The subsurface deformation in the ductile removal regime is composed of plastic flow zone, micro crack zone and median cracks. The ductile deformation mechanism of single crystal GGG during the nanoscratch process is a combination of "material poly-crystallization of nanocrystalline" and "amorphous transformation" with no other forms of crystalline structure found. The generation of median cracks is caused by the severe slip of crystal planes which are subjected to the concentrated stress.