Research on the machinability of A-plane sapphire under diamond wire sawing in different sawing directions

Due to its superior mechanical, optical and chemical properties, sapphire (alpha-Al2O3) is widely used in engineering, optics, medicine, and other scientific research fields. The atomic structure of sapphire gives rise to anisotropy in its mechanical properties, which affects the machinability of sapphire materials on different crystal planes. Different cutting directions will affect the wafer economy and surface quality achieved during wire sawing due to this anisotropy. In this study, the machinability of A-plane sapphire was investigated for diamond wire sawing in three different directions, following the C-plane, R-plane and M-plane. The results show that the direction following the M-plane could be the best direction for diamond wire sawing because this direction results in the minimal sawing forces, the lowest specific energy and the smallest volume of material that will need to be removed during subsequent processing. These characteristics correspond to the direction with the highest fracture strength since the material is removed by brittle machining. The force ratio for sawing in the direction of the R-plane is the smallest because this direction is associated with the minimum hardness and the lowest critical load for the transition from plastic to brittle removal of the workpiece material. The 3D height parameters show no obvious pattern among the three sawing directions. The mechanism of material removal is mainly brittle removal, with some plastic removal, and is obviously affected by the crystal orientation.