Reserch On Constitutive Model And Prediction Of Microstructure For TA15Titanium Alloy In Hot Processing

TA15is a kind of nearly titanium alloy whose performances are similar to BT20titanium alloy developed by Russia.It has high specific strength, creep resistance,corrosion resistance and good welding performance,so it is widely used in aerospaceindustry.In this paper,the constitutive model and the microstructure evolution model ofTA15titanium alloy in the hot processing were established through experiments, based onwhich the forging forming processes and the microstructure prediction of TA15beams,were carried on the finite element simulation.The flow stress-strain curves of TA15are obtained through isothermal compressionexperiment on the TA15titanium alloy. In this paper, the influence laws of temperature,strain rate and strain on flow stress were obtained through a summary of the analysis ofthe stress-strain curves.Considering serious thermal effect of the deformation of TA15titanium alloy, in order to ensure the accuracy of experimental results, the law of heatproduction during the deformation was analyzed. Constant values, such as A, α, and n, andactivate energy Q were obtained through the regression processing of the stress–straincurves under different strains. A set of constitutive equations for TA15titanium alloy wereproposed by using an Arrhenius-type equation. According to the obtained constitutivemodel, the calculated value of the flow stress under different deformation conditions canbe got, and comparing the calculated value and experimental value of stress was to verifythe feasibility of the constitutive model eventually.By means of microstructure analysis under different deformation conditions, themicrostructure changing laws with the temperature, strain rate were summarized.Astatistical analysis on metallograph was to get the size and the volume fraction of theprimary,and the microstructure evolution model of the TA15titanium alloy on hightemperature deformation was established. Through the stress and strain data obtainedduring hot compression, the hot working diagrams under different strain wereacquired.According to the instability figures, the dangerous area of the forging wasdetermined. Based on the analysis of the hot processing diagram and deformationmechanism, the optimum processing craft ranges for TA15titanium alloy were obtained.By using Deform-3D, the forging forming processes of the TA15beams were simulated. According to the result of simulation analysis of the stress, strain and temperature inthe process of forging and the change rules of microstructure prediction model mentionedin the fourth chapter, the volume fraction of the phase in the forging process wasforecasted.