Abstract
Electrochemical micromachining (ECMM) with microtool electrodes is a promising method for microshaping bulk metallic glasses (BMGs) at room temperature. A key challenge is the control of the electrode reactions to impede the disturbing passive layer formation on machined surface regions. In the example case of a Fe-based glassy Fe65.5Cr4Mo4Ga4P12C5B5.5 alloy, it will be demonstrated that by using an aqueous electrolyte based on 0.1 M H2SO4 solution with up to 0.1 M Fe2(SO4)3 addition and by applying ultrashort voltage pulses, complex microstructures can be machined with high precision. Potentiodynamic polarization measurements reveal that the salt addition reduces the charge transfer resistance of the microtool and therefore, the negative bias potential effect. The free corrosion and passive state of the BMG workpiece are affected, but not the transpassive regime. Systematic ECMM studies were conducted to obtain optimum parameters for shaping complex lateral structures with very smooth and well-defined machining areas.
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ACKNOWLEDGMENT
We thank Franziska Karnbach (IFW Dresden) for the scanning electron microscopy investigations, Andreas Freidank for conducting the potentiodynamic polarization experiments and the research division of the IFW Dresden for the design and installation of the micromachining setup. We gratefully acknowledge the German research foundation (DFG) for the support of this work under grant Ge 1106/10.
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Horn, S., Oswald, S., Stoica, M. et al. Complex microshaping of bulk metallic glass surfaces by electrochemical means. Journal of Materials Research 30, 3493–3501 (2015). https://doi.org/10.1557/jmr.2015.336
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DOI: https://doi.org/10.1557/jmr.2015.336