Influence of the high speed milling process on the mechanical and microstrcutural properties of ultrafine grained (UFG) profiles produced by linear flow splitting

In the present work the effects of milling parameters on the surface quality, microstructures and mechanical properties of machined parts having a UFG gradient microstructure are investigated. The effects of the cutting speed, the feed per tooth, the cutting tool geometry and the cooling strategy are shown. It has been found that the surface quality of machined grooves can be improved by increasing the cutting speed. However, cryogenic cooling with CO2 shows no significant improvement of the surface quality. Microstructure and hardness investigations revealed similar microstructure and hardness variations near the cutting edges for both utilized tool geometries. Cryogenic cooling has been found to decrease more far-ranging hardness reductions due to high process temperatures, especially in the UFG regions of the machined parts, whilst it cannot prevent the drop in hardness directly at the cutting edges.