The Study On Hot Deformation Behaviors And Processing Map Of Ti6242s Alloy

Ti6242s titanium alloy is a new near-alpha titanium alloy,self-study designed by BaojiTitanium Industry Co,Ltd,which has a low density,high strength remarkable resistant to hightemperature and corrosion,and good fatigue performance,and so on.The hot deformation behavior,evolution of the microstructure and softening mechanismsof Ti6242s alloy have been studied with the aids of OM and SEM conducted on thermalsimulator testing machine. The processing maps of Ti6242s alloy were established bydynamic materials model and the high temperature deformation characteristics had beenanalyzed using processing map in detail.Conclusions can be drawn as follower:（1）T（α+β）/βphase transition point of Ti6242s alloy was studied by continuous heatingmetallographic method,and T（α+β）/βphase transition point of Ti6242s alloy is1000℃¹010℃.（2）The test discovered the influence of hot deformation parameters on flow stress of thealloy.The results indicated that Ti6242s alloy is sensitive to the variety of strain rate andtemperature,and the flow curves exhibited a peak stress followed by flow softening,and theflow softening behavior is more evident with the decrease of deformation temperature.Athigher strain rate,typically1¹0s-1,discontinuously yielding followed by flow oscillations wasobserved in β phase region.The phenomenon can be explained by dynamic theory.It has beengenerally accepted that this phenomenon was associated with the sudden generation of newmobile dislocation from grain boundary sources.（3）The thermal deformation behavior of titanium alloy was studied by thethermal/mechanical compression simulation experiment,analysis the effect of thermaldeformation parameters on flow stress of the alloy during high temperature deformation andcombining with hot compression true stress-true strain curves,material constants of hightemperature deformation of the alloy was obtained,A new hyperbolic sine constitutiveequation has been firstly established using the parameters of Zener-Holloman,and hotdeformation activation energy and deformation parameters have been obtained.The constitutive equation can perfectly describe the steady-state flow stress of Ti6242s alloy andwas verified by the experiment very well.（4）The softening mechanisms during hot deformation for Ti6242s alloy were alsostudied.The primary mechanism was dynamic reversion for the deformation above transitiontemperature.Lamellar structures tend to spheroid when the alloy deformed below transitiontemperature,the spheroidization mechanism proposed by Margo lin and Cohen mainly wassegregation of grain boundaries.（5）The processing map of Ti6242s alloy was established on the basis of the dynamicmaterial model,to determine the optimum deformation process is:T=975℃,=0.01⁰.1s^-1.