On the surface characteristics of a Zr-based bulk metallic glass processed by microelectrical discharge machining

Microelectrical discharge machining (micro-EDM) performance of a Zr-based bulk metallic glass was investigated experimentally. Various discharge voltages and capacitances were used to study their effects on the material removal rate, cross-sectional profile, surface morphology and roughness, carbonization, and crystallization. Experimental results indicated that many randomly overlapped craters were formed on the EDMed surfaces, and their size and distribution were strongly dependent of the applied voltage and capacitance as well as their positions (center region or outer region), which further affected the surface roughness. Raman spectra and energy dispersive X-ray spectroscopy demonstrated that amorphous carbons originating from the decomposition of the EDM oil were deposited on the EDMed surface. Although some small sharp peaks appeared in the X-ray diffraction patterns of the micro-EDMed surfaces, a broad hump was maintained in all patterns, suggesting a dominant amorphous characteristic. Furthermore, crystallization was also affected by experimental conditions and machining positions. Results in this study indicate that micro-EDM under low discharge energy is useful for fabricating bulk metallic glass microstructures or components because of the ability to retain an amorphous structure.