Micromiling of coarse-grained and ultrafine-grained Cu99.9E: Effects of material microstructure on machining conditions and surface quality

This paper investigates the machining response of metallurgically and mechanically modified materials, in particular, coarse-grained (CG) Cu99.9E, with an average grain size of 30 µm and ultrafine-grained (UFG) Cu99.9E, with an average grain size of 200 nm, produced by Equal- Channel Angular Pressing (ECAP). A novel high-precision method for assessing the homogeneity of the material microstructure is proposed based on Atomic Force Microscope (AFM) measurements of the coefficient of friction at the atomic scale, enabling the prediction of the minimum chip thickness of the individual grains inside the bulk. The investigation has shown that by refining the material microstructure, the minimum chip thickness has been reduced and a high surface finish can be achieved. Also, the homogeneity of the material microstructure and the resulting surface quality have been improved.