Study on force-thermal characteristics and cutting performance of titanium alloy milled by ultrasonic vibration and minimum quantity lubrication

Ti-6Al-4V alloys are widely utilized in aerospace field because of its excellent physical and mechanical performance. Nevertheless, titanium alloy has high strength and low thermal conductivity, which leads to poor processability. Therefore, in the titanium alloys cutting processing, decreasing cutting force and cutting temperature are reliable ways to improve its cutting machinability. The high-frequency intermittent cutting effect of ultrasonic vibration be beneficial to reduce the milling force, and the minimum quantity lubrication (MQL) technology can efficiently improve the friction environment and decrease the cutting temperature. Combined with the technological superiority of ultrasonic vibration assisted machining (UVAM) and MQL, this paper proposes to use UVAM&MQL technology for titanium alloy milling. Firstly, theoretical analysis shows that the separation property of UVAM can enhance the cooling/lubrication of MQL, and the coupling action of UVAM and MQL can improve the force and temperature generated in the cutting process. Then, the variation of surface roughness, surface morphology and chip morphology under this force-thermal coupling is discussed through milling experiments, and compared with conventional milling (CM) and UVAM. From the results, we make out that compared with CM, both UVAM and UVAM&MQL can reduce the cutting force. When the cutting speed is high, UVAM can't reduce the cutting temperature, while UVAM&MQL produces a smaller cutting temperature under all parameters. When the UVAM&MQL method is adopted for processing, the surface is smoother, and the surface forms a clear and uniform vibration texture. Compared with CM and UVAM, the surface roughness of UVAM&MQL is decreased by about 27–51 % and 5–44 %, respectively. In addition, UVAM&MQL method is beneficial to promote the transformation of serrated chip to non-serrated chip.