Investigation the effect of strain history on crystallographic texture evolution based on the perspective of macro deformation for high speed machining Ti-6Al-4V

摘要

Control of texture evolution of machined surface is an important goal to achieve specific property of workpiece in one macroscopic direction or plane. The present work aims to explore the comprehensive effect of localized strain on the texture variation during high speed orthogonal cutting Ti-6Al-4V. The strain distribution on machined surface is firstly calculated based on finite element (FE) model. Then electron backscattered diffraction experiments are performed to observe the texture variation formation of Ti-6Al-4V machined surface. The FE simulation results show that the strain distribution of machined surface fits with a negative exponential function and the direction of maximum shear strain towards cutting direction varies in the range of 25-40. Experimental results show that the grain misorientation distribution exhibits a peak at the angle of 30-45, which is consistent with the inclination angle of the maximum shear strain in Ti-6Al.4V machined surface. Pole figures and orientation distribution function maps present that C fiber deformation texture is generated evolving from initial texture component of {10 - 10} (0001). Pyramidal slip system (c + a) of alpha-Ti phase begins to be activated under the effects of high strain rate and cutting temperature with the increasing of cutting speed. The findings suggest that lattice rotations leading to the changes of orientation are the direct consequences of imposed deformation strain on machined surface. The results also provide a new avenue for optimizing cutting parameters to control texture variation of Ti-6Al-4V.