Further insight into the chip formation of ferritic-pearlitic steels: Microstructural evolutions and associated thermo-mechanical loadings

The main objective of this paper is to clarify the deformation mechanisms of ferritic-pearlitic steels in metal cutting and correlate them to the associated thermo-mechanical loadings. Dry orthogonal cutting tests have been performed on a normalised AISI 1045 steel with coated carbide tools. Experimental evidences of a drastic grain refinement process in the main deformation zones are advanced on the basis of optical microscope, Field Emission Scanning Electron Microscope (FESEM) and Electron BackScattered Diffraction (EBSD). Microstructural evolutions leading to a grain size down to 200 nm and fragmented cementite are especially emphasized. A numerical approach is further employed to target and quantify the loadings applied to the machined material and extract further information on the Secondary Shear Zone (SSZ). Strains amplitude appears to be the driving parameter of these evolutions via a dynamic recrystallisation process promoted by an intense and localised heat generation. The present contribution highlights that in-depth and microscale investigations of chip formation including microstructural aspects are still required. (C) 2013 Elsevier Ltd. All rights reserved.