Morphology evolution and micro-mechanism of chip formation during high-speed machining

Abstract

In this paper, the morphology and micro-mechanism of chip formation during high-speed machining aluminum alloy 7050-T7451 is investigated based on the combination of dislocation theory and plastic deformation theory. Experiments of quick stop stoppage for turning and special method (Buda) for milling process were carried out in order to obtain shear angle in different cutting speeds. The results show that effective flow stress and temperature in front edge zone is higher and more concentrated than that in other deformation zones. The shear front-lamellar structure was observed and analyzed in the front edge zone which influences the chip formation directly. The influence of cutting speed on chip formation was analyzed by simulation and experiments. Cutting speed is an important factor affecting the morphology evolution and chip formation. When the cutting speed is below 1500 m/min, the concentration of shear stress and the shear front-lamella structure of cutting deformation are more remarkable and easier for forming continuous ribbon chips. With the cutting speed increase, the ribbon chip transforms into serrated chip when a critical cutting speed (2500 m/min) is reached. Finally, microscopic mechanism of chip formation has been revealed and critical condition of the shear front—the layer structure formation—has been determined.