Surface Integrity Evolution of Zirconium-Based Metallic Glass Multi-Cut with Wire Electrical Discharge Machining

In this paper, wire electrical discharge machining (WEDM) is used to machine zirconium-based metallic glass. Metallic glass is very sensitive to temperature, and the surface of WEDM will crystallize. For machining defects, multi-cutting methods are used to reduce the impact on the machining of metallic glass. The main research is the effects of different cutting passes on the surface morphology, surface roughness, recast layer thickness, surface microhardness, carbonization, and crystallization of a workpiece. Results show that increasing the cutting passes reduces the size of craters and hard convex edges and produces a smoother surface, and the roughness Ra value is reduced from 3.228 to 0.586 μm. After first cutting, the thickness of the recast layer and the heat-affected zone (HAZ) reached 37.4 μm, and many microcracks appeared in the HAZ. The thickness of the recast layer and the HAZ decreased with the increasing the cutting passes. After the fourth cutting, the thickness of the recast layer and the HAZ decreased by 52% compared with the first cutting, and the surface showed a good amorphous state. Moreover, the WEDM is beneficial to improve the surface microhardness of the zirconium-based metallic glass. The hardness is the highest after the first cutting, and an increase in cutting passes will gradually decrease the surface microhardness. Multi-cutting can effectively improve the surface quality, and this processing method provides an effective method for zirconium-based metallic glass machining applications.