Study On Hot Deformation Behavior And Microstructure Evolution Simulation Of Tb17 Titanium Alloy

TB17 titanium alloy is a new type metastable beta titanium alloy with super high strength toughness.The study of the thermal deformation behavior and microstructure evolution of TB17 titanium alloy is of great significance to optimization of processing parameters.In this paper,with the constant temperature and strain rate compression tests,combined with the metallographic analysis system,the high temperature deformation behavior of TB17 titanium alloy was studied,and got the optimum processing range of TB17 titanium alloy by banding with the processing diagram,in the end,DEFORM-3D software was used to simulate the microstructure of thermal compression test of alloy.The main research work was as follows:First of all,with the Gleeble3500 thermal simulation testing machine,a constant temperature and strain rate simulation compression test for TB17 titanium alloy was carried out,the experimental deformation temperature was 800¹000 C,the strain rate was 0.001⁵0s-1,and the strain was 1.2.according to the data of compression test,the constitutive equation of flow stress was established,the activation energy of thermal deformation of the alloy Q=232.579kJ/mol was obtained.At the same time,the flow stress constitutive model was verified.It was found that the model had high accuracy.Combined with metallographic technology,the microstructure evolution rule was analyzed.It was found that the alloy had obvious dynamic recrystallization at low strain rate and a large number of recrystallized grains began to produce from the grain boundary of the beta phase.At high strain rate,the alloy grain was elongated and even broken,and the alloy mainly took dynamic recovery as softening mechanism.Secondly,the processing diagram of TB17 titanium alloy based on Prasad and Murty criteria was constructed.Stable deformation zone:temperature was at800⁸70?degree,the strain rate was at 0.001s^-10.64s^-1;temperature was at870¹000 degree,the strain rate was at 0.001s^-10.82s^-1;when the deformation zone was stable,the alloy had obvious dynamic recrystallization and equiaxed structure;Instable deformation zone:temperature was at 800⁸70 degree,the strain rate was at0.483 s^-150s^-1;temperature was at 870¹000?degree,the strain rate was at0.616s^-150s^-1,in this area,the microstructure of the alloy presented defects like local flow,flatting of a beta grain or even breakage and so on.It was easy to cause instability of TB17 titanium alloy at high strain rate,processing in this area should be avoided in actual hot working.Finally,based on the compression data,the dynamic recrystallization model and dislocation density model of TB17 titanium alloy in the beta phase region were established.The microstructure of TB17 titanium alloy at different strain rates with the strain 1.2 and the temperature 950 degree was simulated on the DERORM-3D platform with cellular automata method.The simulation results showed that the dynamic recrystallization behavior occurred at different parts at the low strain rate(0.01s^-1),the earliest and most sufficient dynamic recrystallization occurred in the large deformation zone,and the grain size was less than that of other regions;The increase of the strain can also promote the occurrence of dynamic recrystallization,grain was obviously refined.With the increase of the strain rate,the recrystallization behavior was not sufficient,but the grain size decrease.The simulation results were of high accuracy and coincide with the experimental results.