Effects of tool vibration on surface integrity in rotary ultrasonic elliptical end milling of Ti–6Al–4V

Abstract

Titanium alloys have been applied in aerospace, biomedical, and chemical industries due to their superior mechanical properties. As a novel machining method, rotary ultrasonic elliptical machining has been successfully introduced into high-speed side milling of Ti–6Al–4V recently. However, the surface integrity in end milling of titanium alloy using this method is still unclear. In this study, a comprehensive experiment on surface integrity in rotary ultrasonic elliptical end milling of Ti–6Al–4V was conducted at various vibration amplitudes and cutting speeds. Results show that regular substantial micro-vibration textures in the form of separated ridges are obtained on the machined surfaces in RUEEM. Surface roughness values rise from Ra 0.160 μm to Ra 0.758 μm with the increasing cutting speed and vibration amplitude. Both the thickness of subsurface deformed layer and the value of surface micro-hardness increase with rising amplitude at low cutting speeds, while the hardening effect gradually weakens as the cutting speed increases to 160 m/min. Besides, the values of surface compressive residual stress gradually decrease with vibration amplitudes at low cutting speeds, while opposite trends show at the high cutting speed (160 m/min). This study can provide a new method for the effective control of the surface integrity for high-speed end milling of titanium alloy.