Micro-machinability of bulk metallic glass in ultra-precision cutting

Mirco-machinability of Zr55Cu30Al10Ni5 bulk metallic glass including surface integrity, cutting force, chip morphology, and toolwearwas investigated by means of ultra-precision cuttingwith a diamond tool and a boron nitride tool. The results showed that the metallic glass only attained the lowest surface roughness of about R-a 100 nm and was difficult to cut to achieve a mirror surface due to its viscous flow even using a depth of cut of 0.6 mu m. An empirical metal micro-cutting force model was applicable for the bulk metallic glass only under the condition that the undeformed chip thickness was larger than the tool edge radius. The diamond tool showed a better wear resistance but a worse machined surface quality as compared to the PCBN tool. TEM observation and nanoindentation analysis indicated that nanocrystallization of the metallic glass and work softening were detected after the micro-machining. Besides, the generation of shear bands and its effect on the machinability of the bulk metallic glass were disscussed. (C) 2017 Elsevier Ltd. All rights reserved.