Effects of crystallographic orientation and negative rake angle on the brittle-ductile transition and subsurface deformation in machining of monocrystalline germanium

In this study, taper cutting experiments using a diamond tool were conducted to investigate the effects of negative rake angle and cutting orientation on the brittle-ductile transition and subsurface deformation of monocrystalline germanium cut on the (100), (101), and (111) planes. Confocal laser scanning microscopy and Raman spectroscopy were used to observe the three-dimensional surface topographies of the samples and characterize the subsurface deformation, respectively. The results showed that the negative rake angle and crystallographic orientation have a significant effect on the brittle-ductile transition and subsurface deformation mechanisms in ductile regime machining of monocrystalline germanium. A large negative rake angle alters the initial surface crack patterns, as well as anisotropic behavior of the ductile-brittle transition and subsurface deformation of monocrystalline germanium.