Analysis on the effect of phase boundary in meso-cutting of AISI1045 based on the microstructure-level simulation

In this paper, in order to discover the mechanism of chip formation in meso-cutting, an equivalent homogenous material (EHM) model and a microstructure-level model based on the real microstructure were built up for finite element analysis (FEA) of the meso-cutting process of hot-rolled AISI1045. The advantage of the microstructure-level model over the EHM ones includes its capability in revealing the hidden phenomena and mechanisms related to grain, grain boundary, and phase structure besides the higher prediction precision. And these phenomena and mechanisms are very important for the correct understanding of meso- and micro-cutting. After experimental verification, the microstructure-level model was used to analyze the effects of phase boundary on the chip morphology, strain, stress, etc. in the meso-cutting. It was found that large strain took place in the interior of the ferrite and built up the plumps on the free chip surface. And large strain gradient formed around the phase boundaries by the combining effects of the generation of geometrically necessary dislocations for meeting the deformation compatibility between grains, image force, and pile-up of dislocations. In addition, the reversal of the strain, stress, and strain rate across the phase boundary was noticed as well. At last, the size effect was analyzed from the perspective of the strengthening of material due to the variation of the hydrostatic pressure with the ratio (λ) of a_p/r_e and its effect on defects along the phase boundaries and shear stress.