Influence of thermal deformation parameters on dynamic recrystallisation behaviour of TB15 titanium alloy
The isothermal thermal compression experiments of TB15 titanium alloy with the deformation temperature of 810-930 ℃,strain rate of 0.001-10 s-1,and reduction of 60％were carried out by thermal simulation compression testing machine to study the influ-ence of thermal deforming parameters on dynamic recrystallization behavior of TB15 titanium alloy.The results show that the stress-strain curves of TB15 titanium alloy with different strain rates exhibit different characteristics,and the flow softening curves show V-shaped char-acteristics with the increase of strain rate.When the strain rate is in the range of 0.001-0.1 s-1,the dynamic recrystallization(DRX)volume fraction and DRX grain size increase with the increase of deformation temperature and the decrease of strain rate,and the increase of DRX grain size is more significant than that of DRX volume fraction.When deformation at low strain rate,the original β grains are di-vided into regular polygonal subgrains by low angle grain boundaries.Continuous dynamic recrystallization is achieved by the transforma-tion of low angle grain boundaries to large angle grain boundaries through continuous absorption of dislocations and progressive lattice rota-tion.With the increase of strain rate,the nucleation position of the recrystallized grains gradually migrates from the internal to the bounda-ries of original β grains,the forming uniform and fine"necklace-like"recrystallized grains are formed in the original β grains boundaries,which makes it easier for discontinuous dynamic recrystallization to occur through the mechanism of grain boundary arch.
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