Deformation Behavior And Softening Mechanism Of Plasma Hydrogenated TiAl Based Alloy

Engine blades need to be used for a long time under high temperature and complex stress,so the performance requirements of the material are very strict.Because of its low density,high specific strength and excellent high temperature oxidation resistance,TiAl alloy is considered to be a new type of lightweight superalloy with the most potential to replace traditional nickel-based superalloys.TiAl alloy is two intermetallic compounds,?-TiAl and?₂-Ti₃Al,which make TiAl have these excellent high temperature properties.At the same time,the material's intrinsic brittleness makes it difficult for TiAl alloy to be produced and applied in batches.As a temporary alloying element,hydrogen was originally used to improve the hot workability of Ti alloys.In recent years,studies have shown that hydrogen as a temporary alloying element can also improve the hot workability of TiAl alloys.In this paper,the effect of hydrogen on the deformation behavior of TiAl alloys and the softening mechanism of hydrogen-induced TiAl alloys during high-temperature deformation are studied by plasma hydrogenation treatment.In this paper,the effect of hydrogen on the phase composition,microstructure and mechanical properties of TiAl alloy at room temperature was first investigated.After the plasma hydrogenation treatment of Ti-48Al-2Cr alloy,its phase composition has not changed,and both are composed of a large amount of?-TiAl and a small amount of?₂-Ti₃Al;after observing the microstructure of the alloy,The?/?₂ lamellar structure of the TiAl alloy after hydrogenation is more fine,and more?single-phase regions are formed at the grain boundaries.Hydrogen exists in the TiAl alloy as a solid solution.The hydrogen content is 0.058wt.%.After the alloy is exposed to hydrogen,the microhardness is significantly improved,the room temperature compressive strength is increased from 1100MPa to 1400MPa,and the maximum deformation at room temperature is increased.The effect of plasma hydrogenation treatment on the high-temperature deformation behavior of TiAl alloy at 1000?-1150?and strain rate of 1s^-1-10^-3s^-1 was studied using a Gleeble thermal simulator.The results show that the flow stress of the material decreases with increasing temperature and decreases with decreasing strain rate,and the material has obvious recrystallization characteristics during thermal deformation.The peak stress of TiAl alloy after plasma hydrogenation treatment was reduced by 32.3%.The constitutive equations of TiAl alloys before and after plasma hydrogenation were established,and the thermal deformation activation energies of TiAl alloys before and after plasma hydrogenation were 526.54kJ/mol and 442.42kJ/mol,respectively.The EBSD observation of the deformed structure of the alloy after thermal deformation shows that after alloy hydrogenation treatment,there are fewer residual lamellae,the recrystallization volume fraction increases,the low dislocation density area increases,and the material deformation is more uniform.Hydrogen-induced dynamic recrystallization of TiAl alloy during thermal deformation and hydrogen-promoted dislocation motion are the main mechanisms of hydrogen-induced TiAl alloy softening at high temperature.