Observation and quantitative characterization of geometric and cyclical features associated with chip segmentation during machining of Ti6Al4V alloy

Chip segmentation is an important type of chip formation during machining of metals. However, there are still inconsistent variation trends in the morphological characteristics and contradictory physical models regarding chip segmentation. To better understand the chip segmentation mechanism during machining of Ti6Al4V, cyclic cutting forces during machining were recorded with a dynamometer, the periodic features on the surfaces of the chip and workpiece were observed with a scanning electron microscope (SEM) and their surface profiles and wear on tool rake face were measured with a 3D measuring laser scanning microscope in the present study. It was found that the periodic/wavy patterns on the machined surfaces of the chip and workpiece are attributed to the periodically distributed dimple/sliding rows with different spacings and heights under various cutting conditions. The observation, quantitative characterization and correlation of the periodic features on the surfaces of the chip and workpiece, cyclic cutting forces and tool wear on rake face provide useful information on how the surfaces of the chips and workpiece, and the cutting forces change during chip segmentation. This will lead to the proposal of a novel model for chip segmentation. X-ray diffraction (XRD) was also carried out to investigate the deformation mechanisms on the machined surface and longitudinal cross-section of the segmented chips. • The periodic/wavy features on the machined surfaces of the chip and workpiece are associated with dimple/sliding rows • The periodic features on the surfaces of the chip and workpiece are correlated • Segment length on the free surface of the chip is shortened at low cutting speeds • Dimples on the side machined surface of the workpiece are formed in front of the cutting edge • Cyclic cutting force is associated with the wavy profile on the side machined surface of the workpiece