Influence of workpiece texture and strain hardening on chip formation during machining of Ti–6Al–4V alloy

Abstract

The results of the investigation on the influence of texture on chip formation during machining of Ti–6Al–4V alloy are reported in this work. Different textures are produced in this alloy by cold-rolling as-received and annealed material to 30–47% reductions. As-received and annealed samples exhibited basal and transverse textures while in cold-worked material, the basal texture disappeared and, a texture component with (0001) pole inclined at 70° from the Z direction was observed. Machining was done in these thermo-mechanically processed plates at a low cutting speed of 0.8 m/min to avoid temperature rise and the consequent microstructural modification. As-received and annealed material exhibited saw-tooth morphology of chips, while samples deformed to cold-work of 40% and above produced continuous chips with fine serrations at the free surface. Machined chips have retained the transverse texture in annealed material with reduced intensity, while the basal texture has disappeared in deformed material. The possible slip systems responsible for the development of these textures were identified using Schmid factors. The difference in morphology of chips between annealed and cold-worked samples is explained based on texture developed during machining, which has a bearing on the strain necessary for fracture initiation in the primary shear zone, thus affecting the spatial frequency of segmentation.