Oxidation and crystallization of Zr-based bulk metallic glass due to machining

Bulk metallic glass was subjected to extreme deformation conditions during machining operation. The flash temperature, oxidation and crystallization within chips from a Zr-based bulk metallic glass were investigated. A near-infrared spectrometer was used to capture the light emission from the tool-chip interface allowing the calculation of the temperature. Very high temperatures in the 2400–2700 K range were observed and associated with the light emission and oxidation in the chips. X-ray diffraction analysis revealed oxidation of chips machined at high cutting speeds. Optical micrographs of polished and etched chip cross-sections showed a dendritic pattern due to crystallization. Using a field emission gun SEM, amorphous and crystalline regions were analyzed. This study demonstrates the oxidation and crystallization of bulk metallic glass during machining.