| Ti-Nb alloy has low elastic modulus,good shape memory effect,excellent biocompatibility,outstanding wear resistance and corrosion resistance.As a result of the above advantages,it is widely used in medical implants,like artificial joints and screws that could be applied to connect human bones or joints.In this paper,hot compression experiments and metallographic microstructure experiments of Ti-Nb alloy were respectively carried out by Gleeble-3500 thermal simulation equipment and FL7500metallographic microscope.The high-temperature deformation behavior and hot working process of Ti-Nb alloy were studied from the flow stress curve,hot deformation activation energy,constitutive relationships and processing maps,Which provides the theory basis for the high-temperature deformation simulation,the improvement of the hot deformation process and the promotion of organizational properties,etc.In this paper,based on the experimental data values,the flow stress curves of Ti-Nb alloy at different deformation conditions were drawn and the hot deformation activation energy values of the studied alloy at the strain of 0.3,0.6,0.9 and 1.2 were calculated.Moreover,hot deformation activation energy maps were constructed at the corresponding strain.The results show that the flow stresses of Ti-Nb alloy could decrease with the decrease of strain rate or the increase of deformation temperature and whole flow stress curves represent dynamic recovery characteristics.In addition,the hot deformation activation energy values of Ti-Nb alloy are not under influence of strain and deformation temperature,but it increases with the decrease of strain rate.Moreover,the average hot deformation activation energy values of Ti-Nb alloy at the above strains are generally higher than the?-Ti self-diffusion activation energy value,which means that dynamic recrystallization behavior may occur during thermal deformation as well as nucleation and growth may be controlled by the self-diffusion of Nb atoms and pinned by Nb atoms.Meanwhile,the traditional Arrhenius strain-compensated constitutive model and its simplified constitutive model were constructed,the traditional strain-compensated physical constitutive model and its modified,simplified constitutive model were also established respectively.Considering the calculation results of correlation coefficient,average relative error value and absolute error value and the workload of constructing the constitutive model,it is found that the simplified Arrhenius strain-compensated constitutive model and the simplified physical basic constitutive model have a unique function to predict the flow stress of Ti-Nb alloy.In addition,the construction processes of this two models are simple and efficient.Especially,the simplified physical basic constitutive model includes physical and metallurgical significance.As a result,it can be used to predict the stress value of Ti-Nb alloy in engineering applications.According to polar reciprocity model and Prasad,Murty principle's dynamic material model,these three processing maps of Ti-Nb alloy at the strain of 0.3,0.6,0.9and 1.2 were plotted accordingly and microstructures were observed.It is concluded that the DMM processing map of Prasad principle is the most suitable for optimizing the thermal processing parameters of Ti-Nb alloy.Especially,the DMM processing maps of the Prasad and Murty principle have shown an outstanding ability to predict the stable region of the studied alloy.Moreover,the Prasad principle's DMM processing map and the PRM processing map are more suitable methods for the prediction of instability region of the studied alloy.The results reveal that the optimal processing domain of Ti-Nb alloy is at the deformation temperature of 880-940?and the strain rate of 10-2-10-1 s-1.In addition,mechanical instability is the major instability form in the instable domain and the deformation mechanism of the studied alloy is mainly dynamic recovery and dynamic recrystallization in the stable domain. |
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