Effect of microstructure evolution on chip formation and fracture during high-speed cutting of single phase metals

Microstructure evolution of materials has an important effect on chip formation and fracture process, which is also essential for revealing the mechanism of high-speed cutting. Complex microstructures would make it difficult in analyzing the deformation procedure during cutting process. As a result, in this study, oxygen-free high-conductivity (OFHC) copper, including coarse grains and single phase, is chosen for workpiece material to be machined with high-speed cutting experiments for revealing the cutting mechanisms. Chips and chip roots of OFHC copper under orthogonal cutting conditions with increasing cutting speeds from 750m/min to 3000m/min are collected. The microstructure and fracture characteristics of collected chips are observed by electron backscatter diffraction (EBSD) and scanning electron microscope (SEM), respectively. The results show that the grain refinement and dynamic recrystallization (DRX) are both generated during the cutting process, which lead to the strengthening of mechanical properties and the fracture transformation from ductile to brittle. This research explains the effect of microstructure evolution, especially the transformation of grain itself, on the chip formation and fracture mechanisms.