The Behavior Characterization And Optimal Identification In Parameter Of Ti-6AL-2Zr-1Mo-1V Alloy In Thermoplastic Deformation

Titanium and its alloy are light structural materials, and they are widely used inmedical field, shipbuilding industry, energy industry, chemical industry, aerospaceindustry, construction and other fields because of their excellent high specific strength,well causticity-resistance and comprehensive mechanical properties. Due to goodforging properties, titanium alloy forgings are the widest used at present. Although theinherent deficiency of forging process exists, for instance grain coarsening in product oftitanium alloy, narrow temperature interval of forging, local overheating and hydrogenuptake and all that. For these reasons, the performance advantages of titanium alloy cannot keep the full function. However, research and practice experience shows thatmicrostructure and mechanical property improved, strength and corrosion resistanceenhanced, performance and dimensional requirements satisfied when forging processparameters are reasonably set.The content studied in this paper is as follows:①Base on the curves of Ti-6Al-2Zr-1Mo-1V alloy which from upsettingexperiments, the orthogonal test was established to analysis the influence extent ofprocess parameters on the true stress.②Through adopting multivariate regression and polynomial fitting, TheArrhenius constitutive equation of Ti-6Al-2Zr-1Mo-1V alloy with variable parameterswas established.③The processing map and the evaluation parameters such as strain ratesensitivity, power dissipation efficiency and instability parameter, the stable andunstable regions of Ti-6Al-2Zr-1Mo-1V alloy were clarified clearly on the basis ofDMM.④A concept about damage incremental ratio in plastic deformation and a methodto find ductile damage critia was brought forward, and the response of ductile damagecritia to temperature and strain rate was uncovered.⑤-curves under different deformation conditions were obtained throughintroducing hard working rate. Combined with the infection criterion of-curves,two potentials were identified as follows: the critical strain and the critical stress ofdynamic recrystallization. Through adopting regression and the metalography of theTi-6Al-2Zr-1Mo-1V alloy, the constitutive equation of the critical strain was established.⑥The true flow stress model of BP neural network was established by MATLABsoftware to forecast the flow stress curves which were not at the experimentalconditions; Then the stable and unstable regions of Ti-6Al-2Zr-1Mo-1V alloy wereclarified once again by forecasting curves, at the same time the stable and unstableregions were verified through the comparison with regions calculated using true stresscurves from the upsetting experiments, then the experimental curves and forecastingcurves were imported into the DEFORM, and the difference of load-displacementcurves were uncovered.