Study of longitudinal-torsional ultrasonic-assisted vibration on micro-hole drilling Zr-based metallic glass

Zirconium-based metallic glass (Zr-based MG) explores extensive applications in biomedicine and micro/nanomaterial fabrication owing to its remarkable combination of high specific strength and excellent corrosion resistance. In order to solve the difficulty of drilling micro-machining Zr-based MG, the longitudinal-torsional ultrasonic-assisted drilling (LTUAD) technique was employed for processing. Through experiments, its feasibility and effectiveness were explored in comparison with traditional drilling (CD). Firstly, in accordance with the Mohr–Coulomb yield criterion, the model for the mean thrust force under ultrasonic vibration assistance was developed, taking into account both the temperature effect and the tension–compression asymmetry of Zr-based MG. Secondly, the study examined the impacts of spindle speed, feed rate, and ultrasonic amplitude on the thrust force, while also discussing the characteristics of the hole exit and hole wall morphology. Finally, the impact of ultrasonic vibration on suppressing crack initiation and propagation was explored based on the free volume theory. Experimental results showed that the mean thrust force in LTUAD Zr-based MG decreased by 3.95–29.12% compared with that in CD, and the deviation of the experimental results from the model was 17.52%. Compared with CD, LTUAD technology significantly reduced the thickness and diameter of the exit round cap and effectively the number of pits caused by material chipping.