Research On Microstructure Of Cutting Titanium Alloy Based On Multi-scale Simulation

Titanium alloy Ti6Al4 V has been widely used in aerospace and other fields due to its high specific strength,light weight,high temperature resistance and good corrosion resistance.In the process of metal cutting,the final performance of formed parts largely depends on the microstructure and chemical composition of the material.Due to the cutting characteristics of Ti6Al4 V,high temperature,large strain and high strain rate are generated in the cutting process,which leads to the dynamic recrystallization(DRX)behavior of the chip and machined surface.However,from the multi-scale simulation research,combined with the cutting experiment,considering that the cutting Ti6Al4 V material is easy to produce serious plastic deformation,which leads to the microstructure evolution of the chip and machined surface.Especially the influence of tool wear on the microstructure of machined surface affects the final quality and performance of products.In this paper,Ti6Al4 V titanium alloy is taken as the research object.Based on the theory of dynamic recrystallization,numerical simulation technology is used to predict the evolution process of microstructure.On the one hand,the finite element(FE)can simulate the macro physical field;on the other hand,the cellular automata(CA)can simulate the evolution of the micro group,so as to build a finite element cellular automata simulation method with complementary advantages.The effects of cutting speed,feed rate and tool wear on the grain refinement of Ti6Al4 V chip and machined surface were studied,and the sensitivity of material multi physical field to grain refinement was analyzed.Firstly,the finite element model based on JMAK dynamic recrystallization theory is established by DEFORM-3D software,and the credibility of the finite element model is verified by orthogonal cutting Ti6Al4 V experiment.At the same time,multi physical field data of Ti6Al4 V chip and machined surface are extracted by reasonable point tracking function as input parameters of cellular automata model.Secondly,combined with thermal activation theory,grain growth kinetics theory and grain boundary critical conditions,the cellular automata model of dynamic recrystallization evolution during cutting Ti6Al4 V was established by introducing dislocation density model,grain nucleation model and grain growth model.The evolution process of dynamic recrystallization was visualized by the coupling model of finite element and cellular automata.The effects of temperature,strain and strain rate on grain refinement were explored.The electron back scattering patterns(EBSD)experiments were carried out on the machined surface of Ti6Al4 V under a group of cutting parameters.Finally,the influence of different cutting speed and feed rate on the grain refinement of chip and machined surface in the process of cutting Ti6Al4 V is studied,and the sensitivity of multi physical field of material to grain refinement is analyzed.At the same time,the influence of tool wear on the grain refinement of machined surface is analyzed by finite element simulation,and the orthogonal test is carried out with the tool with 0 mm,0.15 mm and 0.25 mm flank wear value respectively The experimental results of cutting Ti6Al4 V are consistent with the simulation results.