Orientation dependence in nanocutting of Fe single crystals: A molecular-dynamics study

We study systematically the nanocutting of an Fe single crystal in dependence of the surface orientation and cut direction. We find that in the general case - where the edge dislocations formed at the cutting edge glide obliquely to it - a complex, three-dimensional dislocation network is created. If, however, the edge dislocations formed align with the cutting edge direction, then a simple (two-dimensional) cutting mechanism is realized, in which dislocations glide consecutively without interaction. The shape of the chip is governed by the direction of the activated glide systems. For strong dislocation interaction, a grain boundary may form separating the chip from the workpiece. A cutting hardness is defined; the calculated values are in good agreement with the ploughing hardness measured in scratching simulations. For selected orientations, we find that instead of dislocation plasticity, twinning is activated. This requires smaller cutting forces and the created chip surfaces are smooth.