Modeling of grain refinement in aluminum and copper subjected to cutting

Plane-strain orthogonal cutting has recently been exploited as a means to refine the microstructure of metallic materials from tens of micrometers or greater to a few hundred nanometers. While experimental work has produced a significant body of knowledge with regard to microstructure and properties of machined materials, only a handful of studies can be found in the literature to discuss the microstructural evolution mechanism and to predict grain refinement during cutting. In this paper, dislocation density-based material models are developed to model grain size refinement and grain misorientation during cutting of Al 6061 T6 and OFHC Cu under various cutting conditions. It is shown that the developed CEL finite element model embedded with the dislocation material models captures the essential features of the deformation field and grain refinement mechanism during cutting. The model predicts the grains in the machined chips are refined from an initial size of 50–100 μm to about 100–200 nm for Al 6061 T6 and OFHC Cu at a low cutting speed of about 0.02 m/s with negative rake angle tools. It is shown that a small applied strain, high cutting speed or high cutting temperature will all contribute to a coarser elongated grain structure during cutting.