Investigation on the Machinability in the Micro-Milling of Amorphous Materials

Amorphous materials have been widely used in various industrial areas such as optics, aerospace, sports, and biomedical applications. The fundamental mechanism in machining amorphous materials is different from that in machining metallic materials due to their unique microstructure and mechanical properties. This thesis presents experimental investigations on the machinability in the micro-milling of two typical amorphous materials: Zirconium based bulk metallic glass (Zr-BMG) and BK-7 glass.A three-axis micro-milling machine is developed to perform the machining experiments on Zr-BMG with a spindle speed of up to 105,000 rpm. The effect of cutting conditions on light emission and surface melting in the micro-milling of Zr-BMG is investigated. The microstructure and crystallization of machined surface are characterized using scanning electron microscopy, metalloscope, X-ray diffraction and Energy Dispersive Spectroscopy. The critical cutting conditions that correspond to the onset of surface crystallization are determined. Progressive tool flank wear with respect to the cutting distance with and without coolant is also analyzed. A resonance based two dimensional vibration stage with thin-wall design is developed to perform the vibration assisted micro-milling of brittle BK-7 glass. The dynamic property of the vibration stage is analyzed using the finite element method and experimental identification. The effects of vibration direction, vibration amplitude and frequency on the surface roughness and surface damage are investigated. It is concluded that the vibration applied in the normal direction has a major effect on the improvement of surface quality by enhancing the brittle-ductile transition of the material in the micro-milling process.Mechanical & Aerospace Engineerin