| With high-strength,fatigue strength and excellent hardenability,near p-titaniumTB6 alloy has widely used in aviation and aerospace field.At the same time,Titanium alloy TB6 belongs to difficult-to-deform material and it s microstructure and performance are sensitive to the thermomechnical parameters,results in bad stability of microstructures and properties in actrual forging manufacturing process.In this paper,the hot deformation behaviors of Titanium alloy of forging TB6 were first studied by isothermal constant rate compression tests,then combined with dynamic material model to establish the processing map to optimize the hot working parameters.Then,based on the multiple regression analysis,estabilished constitutive equation,now stress model and recrystallization kinetics.Investigated grain growth behavior of forging TB6 under different heating temperature and holding time.Simulated the forging process of a certain type of a wheel hub used by Deform-3D software.The results as follow:1.A group of stress-strain curves are obtained through the compression tests with the rage of temperature from 750'C to 1050? strain rate from 0.001s-1 to 0.1 s-1 and the max reduction 60-%.Results show that flow stress is sensitive to the deformaion temperature and strain rate.The flow stress increases significantly with the increasing strain rate and decreasing temperature.Especially,at the strain rate of 0.1s-1 with high temperature,under the interactive influence of flow softening and work hardening,the flow stress curve presented a low amplitude vibration.2.According to the experimental data of stress-strain curves,combined with dynamic materials model and Prasad criterion,can obtain the strain rate sensitivity index and efficiency of energy dissipation at different strian,temperature and strain rate to draw the processing maps of titanium alloy of forging TB6.Combined with microstructure observation,microstructure mechanisms of TB6 titanium alloy in instability region were analyzed.The results showed that unstable region occurred at the rang of temperature from 938? to 1048? and stain rate from 0.006s-1 to 0.1s-1,and the deformation parameter is optimal at the temperature of 815? and strain rate of 0.001s-1.3.Utilized multivariable linear regression analysis and the constitutive equation of hyperbolic sine form proposed by Sellars and Tegart to obtain the hot deformation activation energy is 264.351KJ/(mol·?),then establish the hot deformation constitutive equation,flow stress model and recrystallization kinetics model.and the represent the hot deformation constitutive equation as follow:?=9.40136×109[sinh(0.018402?p)]2-53012exp(-264351/RT)4.Investigated the grain growth behavior of Titanium alloy of forging TB6 under different holding time and heating temperature,which is upper than ? phase transformation temperature.With the increment of temperature and holding time,the grain grow up gradually and the grow rate reduce.In the range of 800? to 890?,grain growth exponent(0.25?0.3)and grain growth activation(73.048KJ/mol)are also calculated.The grain growth is:D=e11.9122exp(-1304S/RT)5.The low of change of forging temperature,stress,strain and strain rate was simulated by Deform-3D finite element software,then combined with the analysis of microstructure of forged piece.The results show that the simulation method can good manifest the real low of change of parameters mentioned among the forging process.Observing the grain distribution regular of forging piece,grains of corner angle are very thick and distribute unevenly,should optimize forging process to benefit performance. |
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