Study On Hot Deformation Behavior And Microstructure Evolution Of Ti₃Al-based Alloy

Ti₃Al-based alloys is a kind of low-density with high temperature strength, oxidationresistance and corrosion resistance.At present, there are few investigator make theirstudies focus on the hot deformation behavior of Ti₃Al-based alloy as well as thecombination power dissipation theory and numerical simulation technology. In thispaper, on the basis of isothermal constant strain rate comperession experiment, the hotdeformation behavior had been studied by microstructure analysis and numericalsimulation method, and the influence law of thermodynamic parameters on the flowstress and microstructure change an was studied. These studies have important guidingsignificance for formulating a reasonable heat process of Ti₃Al-based alloys. The mainconclusions are as follows:Flow stress of Ti₃Al-based alloys are sensitive to deformation temperature and strainrate, and show two different characteristices, namely steady flow and flow softening,the flow stress increases with the increase of strain rate and decreasing deformationtemperature. According to the characteristics of the stress and strain data of Ti₃Al-basedalloys, the BP neural network was used to build the constitutive relationship model,Results show that the constitutive relationship model has high prediction accuracy, itcan statisfy the engineering application requirement.The microstructure was the hybrid microstructureα₂+β+ο, at the deformationtemperature below the phase-transition temperature1100℃, strain rate greater than0.1s^-1was observed to the local flow and adiabatic shear banding. In the state of lowstrain rate, the microstructure was more uniform. When the temperature is higher thanphase-transition temperature1100℃, the deformation microstructure is mainly for thegrain and small amount of dynamic recrystallization grain size. When at lower strainrate, there may be sub-grains in original grain. When at lower strain rate as well as hightemperature, sub-grains merge and grow into larger grains. When at lower strain rate,the grain size of the grains are elongated, grains deform mainly by intergranular localdeformation, easy to cause tissue mechanical instability. Overall, the best deformationconditions are as follows: below1s^-1in the rage of all processing deformationtemperature, in the range of0.001⁰.01s^-1at1100¹200℃or just about1000℃.With power dissipation map theory and numerical simulation technique, we studiedthe thermodynamic parameters on the effect of Ti₃Al-based alloy in the the simulationprocess with the use of the Deform-3D finite element simulation software.Through two development, we put the power dissipation map information into the finite elementsoftware post-processing, so it can intuitive display of the forming properties of thedifferent locations. Organized verify show that the calculated of results are in goodagreement.