On the wire EDM of metastable atomic structured bulk metallic glasses

Bulk metallic glasses (BMGs) are a new class of alloys with metastable amorphous atomic structures, exhibiting attractive properties such as high strength and hardness, and are usually categorized as difficult-to-cut materials. The processing of BMGs is important before their widespread engineering applications. In this work, the wire electrical discharge machining (WEDM) performance of a Zr-based BMG was investigated, as compared with heat-treated BMGs (HBMGs) with partially crystallized atomic structures and industrial pure zirconium (Zr702). Overall, both BMG and HBMG exhibited better cutting efficiency (CE) than Zr702, and the BMG had the best surface roughness. Both the CE and surface roughness of BMG were significantly dependent on the unique physical properties, inheriting from the metastable atomic structures. The effects of six processing parameters on the CE and surface roughness (Ra) of the BMG were examined. The findings shown that the CE was significantly affected by the pulse type (GP), pulse-on time (ON), pulse-off time (OFF), and power tubes (IP), while the surface roughness (Ra) was mainly affected by the pulse type (GP), pulse-on time (ON), and power tubes (IP). Although it is known that the metastable atomic structures could be influenced by the high temperature resulting from sparking, the present findings have validated the feasibility to process metastable atomic structured BMGs using EDM techniques. This work also shows that it is possible to achieve both high CE and low surface roughness during WEDM with appropriate processing parameters, especially the selection of pulse type (GP) and pulse-off time (OFF). The present findings give more insight into the WEDM mechanisms on the processing of amorphous alloys and open up a useful avenue for the machining of BMG and BMG components for practical engineering applications.