| TA5 titanium alloy is a kind ofαtitanium alloy with high strength,outstanding weldability and corrosion resistance.It is often used as parts under 400°C and in corrosive environments.The isothermal constant strain rate compression test of TA5 titanium alloy was carried out by Gleeble-3800 thermal simulator at deformation temperature 850～1050°C,strain rate 0.001～10 s-1 and maximum deformation degree 60%.The hot deformation mechanism,microstructure evolution and hot working process of TA5 titanium alloy were studied by flow stress curve,constitutive model,processing map and response surface method,which provided theoretical basis for the optimization of hot working process parameters and control of organizational properties of the alloy.In this paper,based on the experimental data,the flow stress curves of TA5 titanium alloy at different deformation temperatures and strain rates were drawn.The results show that the flow stress has positive strain rate sensitivity and negative temperature correlation,and most of the curves show steady-state flow characteristics.The peak stress of the alloy is more sensitive to the strain rate at low temperature.At the same time,the Arrhenius constitutive model and physical constitutive model considering strain compensation were constructed respectively.The correlation coefficient R of the two different constitutive models are 0.993 and 0.990.The average relative error（ARRE）are 4.43%and 8.95%.The Arrhenius constitutive model based on strain compensation is more effective in describing and predicting the flow stress behavior of TA5 titanium alloy by comprehensive analysis.According to the Prasad instability criterion’s dynamic material model（DMM）and the polarity interaction model（PRM）,the DMM and PRM processing maps under different strains were drawn.By comparing and analyzing the unstable zone and the stable zone in the two different processing maps,it is found that the prediction of PRM processing maps is more accurate.The results show that the instability zone of TA5 titanium alloy is 850～970°C,the strain rate 1～10 s-1.The main instability mechanism is local flow.The stable region is the deformation temperature 870～990°C,the strain rate 0.01～0.12 s-1.There is no obvious instability phenomenon in the microstructure of this parameter region,and the main deformation mechanisms are dynamic recovery and dynamic recrystallization.Finally,the response surface model between processing parameters（deformation temperature,strain rate,strain）and material parameters（activation energy,Z parameter,power dissipation efficiency）were established by response surface method,and the interaction effects of different processing parameters on material parameters were analyzed.Based on multi-objective visualization optimization,the optimized processing parameters were obtained.The results show that the established response surface models with different material parameters have high correlation coefficient and prediction accuracy,and the optimized hot processing parameters are as follows:the deformation temperature are850～990°C,the strain rate 0.004～0.15 s-1,which are close to the stable region of PRM processing map,indicating that the method is feasible to determine and optimize the processing parameters of TA5 titanium alloy in the actual production. |
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