Microstructure Simulation Of TC4 Alloy Based On DEFORM-3D

As the most widely used titanium aloy,TC4 titanium aloy has been paid close attention to by domestic and foreign scholars for a long time.With the continuous progress of production and design concept in the new era,more stringent requirements for the production of materials have been put forward.In order to meet the requirements of production,it is necessary to make a more comprehensive study of TC4 alloy.In this paper,the isothermal compression test of TC4 aloy was carried out by the hotsimulation machine of Gleeble-1500.By analyzing the flow stress curve and alloy phase diagrams obtained by hot pressing experiment,the process performance change and microstructure evolution law of TC4 alloy during hot pressing were investigated,and the dynamic recrystallization behavior of TC4 alloy in different phases was studied by simulation software DEFORM-3D.Based on the data of flow stress curves of TC4 alloy in different phase areas obtained by hot pressing test,the constitutive equation of high temperature deformation of TC4 alloy,α+β phase region and β single phase zone was constructed respectively.By introducing the temperature compensated strain rate factor Z and by fitting the linear correlation between the lnZ and the lnσ,the reliability of the constitutive equation for describing the thermal deformation behavior of TC4 titanium alloy was verified.Based on the thermal processing theory proposed by Prasad and others on the basis of dynamic material model（DMM）,the thermal processing diagrams of TC4 alloy have been constructed.The fact that the TC4 alloy is suitable for the dynamic material model（DMM）can be verified by the good linear relationship between the natural logarithm of the strain rate and the stress at fixed temperature.Through the analysis of hot working drawings,the following conclusions are drawn: The instability zone in two-phase region is T=800℃⁸70℃,? =0.1s^-110s^-1;The instability zone in the single-phase region is T=980℃¹100℃,? =5s^-110s^-1;The best processing area for two-phase region is T=880℃⁹20℃,?=0.001 s^-10.003 s^-1;The best processing area of near β is T=960℃⁹70℃,? =0.03s^-10.3s^-1.The analysis of microstructure in alloy phase diagrams proved the conclusion of hot working drawing.In this paper,the dynamic recrystal ization volume fraction constitutive model of TC4 alloy in two phase region was constructed based on the flow stress curve data of TC4 alloy in hot phase test.The constitutive model was introduced into the simulation software DEFORM-3D,The change regulation dynamic recrystallization volume fraction of the TC4 alloy in the two phase region has been obtained by simulation: When the thermal deformation condition is constant,the increase of temperature,the decrease of strain rate and the increase of strain will promote the dynamic recrystallization behavior of the alloy.In the same sample,the dynamic recrystal ization between different deformation zones also has regular difference.The reliability of the dynamic recrystal ization volume fraction constitutive model was verified by comparing the simulated results with the corresponding microstructure in the alloy phase diagrams.In this paper,the dynamic recrystal ization volume fraction model of single phase zone in alloy was obtained by calculating the flow stress curve data of TC4 single phase zone.Based on the analysis of the alloy phase diagrams obtained by experiments,the average grain size of dynamic recrystallization under different conditions was calculated,and then the constitutive model of dynamic recrystallization grain size of TC4 alloy single phase zone was constructed.The constitutive model were simulated in the software and the simulation results were analyzed.The dynamic recrystal ization volume fraction and recrystallization grain size of the aloy single phase region were investigated: The volume fraction of dynamic recrystal ization and the grain size of dynamic recrystal ization increase with the increase of temperature,and increase with the decrease of strain rate.In the different regions of the same sample,the dynamic recrystallization volume fraction and the dynamic recrystal ization grain size distribution have a certain rule,that is,the volume fraction of dynamic recrystal ization is larger,the grain size is relatively smal.The simulated dynamic recrystal ization average grain size was compared with the average grain size in the alloy phase diagram obtained by hot pressing experiment.The error was less than 7%,and the reliability of the dynamic recrystal ization grain size model was verified.In this paper,the dynamic recrystallization process of TC4 alloy in single phase region was simulated by using the dislocation density model in simulation software DEFORM-3D based on the CA method.Combining the simulation results with the aloy phase diagram,the dynamic recrystallization law of the alloy during hot pressing was investigated: With the continuous increase of the strain,the dynamic recrystallization behavior of the material also persists,in the process of new grain continuously in the grain boundary nucleation DEFORM-3D and growth,final grain inside the material showing uniform refinement.