Surface feature and material removal in ultrasonic vibration assisted slot-milling of Ti–6Al–4V titanium alloy

The continuous optimization of processing technology and evaluation methods is an important way to achieve high processing quality and processing efficiency for difficult-to-process materials. To solve the problem of frequent defects on the slot, the ultrasonic vibration assisted slot-milling (UVASM) technology was developed for processing titanium alloy. Simultaneously, comparative experiments were carried out between UVASM and conventional slot-milling (CSM), in terms of surface features of slot bottom and slot sidewall, cutting force, tool trajectory, chip morphology, and micro-hardness. The results show that uniform vibration micro-texture could significantly improve surface topography of slot bottom in UVASM, while numerous tool feed trajectories and observable machining defects detract from the surface quality in CSM. The UVASM can greatly reduce material spalling and edge breakage, thereby maintaining a smooth and regular edge profile of slot sidewall. The tool tips trajectories of two machining methods are highly corresponding to the machining textures of the slot sidewall surface. There is a high-frequency and small-amplitude force fluctuation signal on the axial force waveform in UVASM, which can reduce the instantaneous maximum milling force and milling force in the stable stage by 8.7% and 12.2%, respectively. The UVASM has a better chip breaking effect and surface anti-scratch effect and the UVASM can obtain higher surface micro-hardness and deeper plastic deformation layer than those of CSM. In summary, the multi-dimensional evaluation of slot processing status has been completed and the processing quality of the slot has been improved.