STRAIN EVALUATION MODEL OF ADIABATIC SHEAR-BAND PRODUCED BY ORTHOGONAL CUTTING IN HIGH-STRENGTH LOW-ALLOY STEEL

An evaluation model is proposed for the strain and strain rate of a lo calised deformation band produced by an orthogonal cutting test upon a high strength low alloy steel tempered at 600 degrees after quenching . It can be used to determine the strain and strain rate at the first deformed zone (FDZ) in the chip and also at the second deformed zone ( SDZ) at the bottom of the chip. These zones were severely deformed at high strain rates up to 4.6 x 10(4) - 4.2 x 10(6) s(-1). with strains as high as 1190-2760%. X-ray diffraction showed that the SDZ consisted of ferrite and retained austenite which was not detected in the matri x. Transmission electron microscopy and X-ray diffraction showed that cell structures in the SDZ and FDZ were of nanocrystalline 'grains' wi th a high dislocation density at the 'grains' boundaries. The X-ray di ffraction analysis served to check the validity of the strain evaluati on model. (C) 1996 The Institute of Materials.