Analyzing the effect of elliptical vibration assistance in machining of Zr-based BMG

Abstract

Bulk metallic glasses (BMGs) are known as amorphous metal alloys that have a distinct advantage compared to crystalline metal alloys due to fewer microstructural defects. Elliptical vibration-assisted machining (EVAM) is a promising technique to improve the machining performance of high-strength materials. This paper addresses a knowledge gap by investigating the chip formation mechanism in EVAM of Zr-BMG considering the shear localization due to its amorphous structure. A coupled thermo-mechanical model including the effect of vibration kinematics on Zr-BMG deformation mechanics is proposed. The effects of tool-workpiece separation, speed ratio, and strain rate on shear stress, temperature, and free volume variations due to chip segmentation are predicted and analyzed. The predicted chip formation from the developed model is validated through the comparison of chip morphology with experimental results of EVAM of Zr-BMG. The model reveals the underlying mechanism of material deformation during EVAM of Zr-BMG. According to the simulations and experimental results, the shear localization phenomena in EVAM is delayed due to insignificant changes in free volume, and enhanced heat dissipation resulted in lower temperatures in the cutting zone caused by tool-workpiece separation. Compared to traditional machining, the disparity in temperature generation and free volume diffusion in EVAM reduces as the speed ratio increases. The suppressed accumulation of periodic shear and thermal stresses at the tool tip increases the tool life in EVAM compared to the fractured tool tip in traditional machining.