Study On Hot Deformation Behavior And Processing Map Of A New β Titanium Alloy Based On Friction Correction

β titanium alloys are widely concerned by scholars at home and abroad due to their attractive properties of good cold working property, hot and cold formability and excellent strength-plastic matching after heat treatment. The study on hot deformation behaviors and hot processing maps of the new β titanium alloy have great significance on the guide of hot working process design and microstructure-properties optimization of the same kind of alloy.In this paper, a newly-designed β titanium alloy was researched according to the thermal simulation compression test, and the thermal deformation behaviors of the alloy were studied based on the friction correction. Then, constitutive models and hot processing maps at different true strains were established based on the Arrhenius equation and Prasad criterion. And combined with the analysis of the microstructure and mechanical properties, the optimum hot deformation process parameters of the new alloy were optimized.The flow stress curves of the alloy were modified by friction. And combined with the polynomial fitting of the material parameters, the strain dependent constitutive equations at different true strains were established. When the true strain is 0.3, the stress level parameter of the alloy is 0.017737, the stress exponent is 1.9651, the thermal deformation activation energy is 175.8228 kJ/mol and the structure factor is 0.75×106 s^-1.The average value of thermal deformation activation energies at different true strains is about 174.48 kJ/mol, which is much larger than the self diffusion activation energy of the pure titanium beta phase. Therefore, not only dynamic recovery but also dynamic recrystallization may occur. The strain dependent constitutive equations consideringpartial friction correction had higher accuracy. The mean relative absolute error between the experimental stress value and the predicted flow stress is only 6.598%. While without consideration of the friction correction and effective strain, the value is 8.633%.The microstructure evolution and properties of the alloy under different thermal deformation parameters were researched by using optical microscope and Vivtorinox digital micro hardness tester. The results show that the increase of the deformation temperature can promote the recrystallization and the grain size increases. The average grain size is 8 μm at 700℃ and the size is 44 μm at 1150℃. While the microhardness increases first and then decreases, and it achieves the peak value at 900℃（287.4 HV）.The grain size can be refined by increasing the strain rate, and the average grain size is reduced from 174 μm(0.001 s^-1) to 76 μm(1 s^-1). The microhardness increases with the increase of strain rate, and the peak value is 289.5 HV(1 s^-1). With the deformation degree increases from 30% to 60%, the grain size can also be refined. The average grain size is reduced from 129 μm to 44 μm. The microhardness of the alloy increases with the increase of deformation degree, and the peak value is 318.2 HV.According to hot processing map theory, the hot processing maps of the alloy at different true strains based on Prasad criterion were drawn, and the flow instability zones and safety processing zones were determined. The results show that the parameters of the instability region in the whole process are 700¹110℃ and 0.05¹ s^-1.In this region, material may appear plastic instability and form adiabatic shear band.There are three local maximum regions of power dissipation efficiency in public safety zone. Combined with the microstructure and mechanical properties, in this experiment condition, the optimum hot deformation process parameters of the new β titanium alloy were determined: T =900℃、（ε|.） =0.01s^-1.