Machinability of BMG

Abstract

This chapter covers the series of machinability evaluation test result and discussions of Zr52.5Ti5Cu17.9Ni14.6Al10bulk metallic glass (BMG). These tests are lathe turning, drilling, milling and preliminary level grinding tests. In the continuous machining methods such as turning, drilling and grinding of BMG, above a threshold cutting speed, the low thermal conductivity of BMG leads to chip temperatures high enough to cause the chip oxidation and associated light emission. The high temperature produced by this exothermic chemical reaction causes crystallization within the chips. Chips morphology suggests that increasing amounts of viscous flow control the chip-removal process. Moreover, viscous flow and crystallization can occur during the machining of the bulk metallic glass, even under the high temperature gradient and strain rate. High cutting speed significantly reduced the forces for BMG machining due to thermal softening. However, in intermittent cutting process which is milling, there is no high temperature problem, special burr formations the rollover and the top burr were observed along the slot and achieved good surface roughness, Ra= 0.113 μm, using conventional WC-Co cutting tool. In each method, tests repeated for the conventional materials for comparison purpose. This study concludes the precision machining of BMG is possible with the selection of feasible tools and process parameters for each method.