Experimental and finite element analysis of machinability of AL-6XN super austenitic stainless steel

This paper presents a finite element cutting modelbased on physical microstructure to investigate the thermomechanicalbehaviour of AL-6XN Super AusteniticStainless Steel in the primary shear zone. Frozen chip rootsamples were created under dry turning operation to observethe plasticity behaviour occurring in the shear zones to comparewith the model for analysis. Chip samples were generatedunder cutting velocities at 65 and 94 m/min, feed rate at0.2 mm/rev and depth of cut at 1 mm. Temperature on thecutting zone was recorded by infrared thermal camera.Secondary and backscatter electron detectors were used toinvestigate the deformed microstructure and to calculate theplastic strain. Experimental results showed the formation ofmicrocracks (build-up edge triggers) at the chip root stagnationzone of both samples. The austenite phase patterns wereevident against the cutting tool tip in the stagnation zone of thechip root fabricated at 65 m/min. The movement of thesepatterns caused the formation of the slip lines within thegrains. The backscatter diffraction maps showed the formationof special grain boundaries within the slip lines, workhardeninglayer and in the chip region. Strain measurementsin the microstructures of the chip roots fabricated at 94 and65 m/min showed high values of 6.5 and 5.7 (mm/mm) respectively.The finite element model was used to measure thestress, strain, temperature and chip morphology. Numericalresults were compared to the outcomes of the experimentalwork to validate the finite element model. The model validatingprocess showed good agreement between theexperimental and numerical results, and the error values werecalculated. For a 94- and 65-m/min cutting speeds, 7.5 and5.2% were the errors in the strain, 3 and 2.5% were the error inthe temperature and 4.7 and 6.8% were the error in the shearplane angles.