Dissolution characteristics of metallic glass in aqueous and alcohol-based electrolytes for electrochemical micromachining

Metallic glass (MG), owing to its amorphous and grain-boundary-free structure, holds strong potential as an advanced material for micro-nano manufacturing. However, its high thermal sensitivity often results in crystallization during conventional machining, posing challenges for achieving high precision and surface quality. Electrochemical micromachining (ECMM) offers a promising non-thermal approach for the precise fabrication of MG microstructures. In this study, wire electrochemical micromachining (WECMM) was employed to systematically investigate the electrochemical dissolution and machining behavior of MG-Ni₇₂Cr₁₉Si₇B₂ in aqueous and alcohol-based electrolytes, with particular emphasis on the NaNO₃–ethylene glycol (EG) system. Open-circuit potential and polarization analyses revealed that NaNO₃ promotes compact passive film formation, whereas the NaNO₃–EG electrolyte broadens the passive potential range and suppresses excessive film growth through complexation effects. Electrochemical impedance spectroscopy (EIS) confirmed reduced ionic transport resistance and lower charge-transfer impedance in NaNO₃–EG. WECMM experiments further demonstrated a quantitative improvement in machining precision, achieving a slit width reduction of 8.3 % (18.29 μm vs. 19.95 μm) and significantly fewer adhered products compared with the aqueous NaNO₃ system. Moreover, complex three-dimensional microstructures were successfully fabricated in NaNO₃–EG electrolyte. This study establishes a clear link between the electrochemical behavior and machining performance of Ni-based MG in alcohol-based electrolytes, offering practical insights into improving machining precision and surface quality.