Twinned-serrated chip formation with minor shear bands in ultra-precision micro-cutting of bulk metallic glass

Bulk metallic glasses (BMGs) have unique properties due to their amorphous atomic structure such as excellent mechanical and thermal performances; BMGs are considered to be promising materials for many engineering applications. However, it is important to investigate the cutting mechanisms of BMG in ultra-precision micro-cutting (UPMC). This study focuses on experimental and theoretical investigations on the chip formation in UPMC of BMG. It was firstly found that twinned-serrated chips (TSCs) are generated in UPMC of BMG. The intrinsic cause is that BMG exhibits significant adiabatic effect, which was confirmed by a proposed finite element model. A series of ultra-precision micro-cutting tests have been carried out to verify the results of simulation and reveal the effect of rake angle on the cutting process of BMG. The simulation and experiment of chip formation proved that the adiabatic effect is the key factor to generate the serrated chips in the UPMC of BMG. In addition, there existed twinned shear in one cyclic of each serrated chip. The comparison between simulation and experiment under the machining condition of different tool rake angles showed that the serrated chip and cutting force are sensitive to the rake angle of tool.